aarch64, testsuite: Allow ldp/stp on SVE regs with -msve-vector-bits=128

aarch64, testsuite: Allow ldp/stp on SVE regs with -msve-vector-bits=128

Later patches in the series allow ldp and stp to use SVE modes if
-msve-vector-bits=128 is provided.  This patch therefore adjusts tests
that pass -msve-vector-bits=128 to allow ldp/stp to save/restore SVE
registers.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/sve/pcs/stack_clash_1_128.c: Allow ldp/stp saves
	of SVE registers.
	* gcc.target/aarch64/sve/pcs/struct_3_128.c: Likewise.