math: xfail some cospi tests for ibm128-libgcc

math: xfail some cospi tests for ibm128-libgcc

On powerpc math/test-ibm128-cospi shows:

testing long double (without inline functions)
Failure: cospi_downward (-0xf.ffffffffffffbffffffffffffcp+1020): Exception "Invalid operation" set
Failure: cospi_downward (-0xf.ffffffffffffbffffffffffffcp+1020): Exception "Overflow" set
Failure: cospi_downward (-0xf.ffffffffffffbffffffffffffcp+1020): errno set to 33, expected 0 (unchanged)
Failure: Test: cospi_downward (-0xf.ffffffffffffbffffffffffffcp+1020)
Result:
 is:         qNaN
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0
Failure: Test: cospi_downward (0x3.fffffffffffffffcp+108)
Result:
 is:          9.99999999999999999999999999995574e-01   0x1.ffffffffffffffffffffffff4c8p-1
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0
 difference:  4.42501664022411309598141492088312e-30   0x1.670000000000000000000000000p-98
 ulp       :  179.5000
 max.ulp   :  4.0000
Failure: Test: cospi_downward (0x3.ffffffffffffffffffffffffffp+108)
Result:
 is:          9.99999999999999999999999999996524e-01   0x1.ffffffffffffffffffffffff730p-1
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0
 difference:  3.47591836363008326759542899077727e-30   0x1.1a0000000000000000000000000p-98
 ulp       :  141.0000
 max.ulp   :  4.0000
Failure: Test: cospi_towardzero (-0x3.fffffffffffffffcp+108)
Result:
 is:          9.99999999999999999999999999852310e-01   0x1.ffffffffffffffffffffffe8990p-1
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0
 difference:  1.47689552599346303944427057331536e-28   0x1.767000000000000000000000000p-93
 ulp       :  5991.0000
 max.ulp   :  4.0000
Failure: Test: cospi_towardzero (-0x3.ffffffffffffffffffffffffffp+108)
Result:
 is:          9.99999999999999999999999999952569e-01   0x1.fffffffffffffffffffffff87c0p-1
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0
 difference:  4.74302619264133348003801799876275e-29   0x1.e10000000000000000000000000p-95
 ulp       :  1924.0000
 max.ulp   :  4.0000
Failure: Test: cospi_towardzero (0x3.fffffffffffffffcp+108)
Result:
 is:          9.99999999999999999999999999852310e-01   0x1.ffffffffffffffffffffffe8990p-1
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0
 difference:  1.47689552599346303944427057331536e-28   0x1.767000000000000000000000000p-93
 ulp       :  5991.0000
 max.ulp   :  4.0000
Failure: Test: cospi_towardzero (0x3.ffffffffffffffffffffffffffp+108)
Result:
 is:          9.99999999999999999999999999952569e-01   0x1.fffffffffffffffffffffff87c0p-1
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0
 difference:  4.74302619264133348003801799876275e-29   0x1.e10000000000000000000000000p-95
 ulp       :  1924.0000
 max.ulp   :  4.0000
Failure: Test: cospi_upward (-0x3.fffffffffffffffcp+108)
Result:
 is:          9.99999999999999999999999999852323e-01   0x1.ffffffffffffffffffffffe899bp-1
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0
 difference:  1.47673235656615530277812119019587e-28   0x1.766568e20369c00000000000000p-93
 ulp       :  5990.3382
 max.ulp   :  4.0000
Failure: Test: cospi_upward (-0x3.ffffffffffffffffffffffffffp+108)
Result:
 is:          9.99999999999999999999999999952583e-01   0x1.fffffffffffffffffffffff87cbp-1
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0
 difference:  4.74136253815267677203679334037676e-29   0x1.e0d4cf1e9076600000000000000p-95
 ulp       :  1923.3252
 max.ulp   :  4.0000
Failure: cospi_upward (0xf.ffffffffffffbffffffffffffcp+1020): Exception "Invalid operation" set
Failure: cospi_upward (0xf.ffffffffffffbffffffffffffcp+1020): Exception "Overflow" set
Failure: cospi_upward (0xf.ffffffffffffbffffffffffffcp+1020): errno set to 33, expected 0 (unchanged)
Failure: Test: cospi_upward (0xf.ffffffffffffbffffffffffffcp+1020)
Result:
 is:         qNaN
 should be:   1.00000000000000000000000000000000e+00   0x1.000000000000000000000000000p+0