rs6000: Fix typos in float128 ISA3.1 support

rs6000: Fix typos in float128 ISA3.1 support

The recent float128 ISA3.1 support (r12-1340) has some typos,
it makes the libgcc build fail if it's with one binutils
(assembler) which doesn't support Power10 insns.  The error
looks like:

Error: invalid switch -mpower10
Error: unrecognized option -mpower10
... [...libgcc/shared-object.mk:14: float128-p10.o] Error 1

What this patch does are:
  - fix test target typo libgcc_cv_powerpc_3_1_float128_hw
    (written wrongly as libgcc_cv_powerpc_float128_hw, so it's
     going to build ISA3.1 stuffs just when detecting ISA3.0).
  - fix test used for libgcc_cv_powerpc_3_1_float128_hw check.
  - fix test option used for libgcc_cv_powerpc_3_1_float128_hw
    check.
  - remove the ISA3.1 related contents from t-float128-hw.
  - add new macro FLOAT128_HW_INSNS_ISA3_1 to differentiate
    ISA3.1 content from ISA3.0 part in ifunc support.

Bootstrapped/regtested on:
  - powerpc64le-linux-gnu P10
  - powerpc64le-linux-gnu P9 (w/i and w/o p10 supported as)
  - powerpc64-linux-gnu P8 (w/i and w/o p10 supported as)

libgcc/ChangeLog:

	* configure: Regenerate.
	* configure.ac (test for libgcc_cv_powerpc_3_1_float128_hw): Fix
	typos among the name, CFLAGS and the test.
	* config/rs6000/t-float128-hw (fp128_3_1_hw_funcs, fp128_3_1_hw_src,
	fp128_3_1_hw_static_obj, fp128_3_1_hw_shared_obj, fp128_3_1_hw_obj):
	Remove.
	* config/rs6000/t-float128-p10-hw (FLOAT128_HW_INSNS): Append
	macro FLOAT128_HW_INSNS_ISA3_1.
	(FP128_3_1_CFLAGS_HW): Fix option typo.
	* config/rs6000/float128-ifunc.c (SW_OR_HW_ISA3_1): Guard this with
	FLOAT128_HW_INSNS_ISA3_1.
	(__floattikf_resolve): Likewise.
	(__floatuntikf_resolve): Likewise.
	(__fixkfti_resolve): Likewise.
	(__fixunskfti_resolve): Likewise.
	(__floattikf): Likewise.
	(__floatuntikf): Likewise.
	(__fixkfti): Likewise.
	(__fixunskfti): Likewise.