[PR51534] [arm] split out pr51534 test for softfp

[PR51534] [arm] split out pr51534 test for softfp

The test uses arm_hard_ok and arm_softfp_ok as if they were mutually
exclusive, but they test whether the corresponding -mfloat-abi= flag
is usable, not whether it is in effect, so it is possible for both to
pass, and then the test comes out with incorrect expectations
whichever the default float-abi is.

Separate the test into hard and softfp variants, and extend the softfp
variant to accept both ARM and Thumb opcodes; it unwarrantedly assumed
the latter.

for  gcc/testsuite/ChangeLog

	PR target/51534
	* gcc.target/arm/pr51534.c: Split softfp variant into...
	* gcc.target/arm/pr51534s.c: ... this, and support ARM too.