testsuite, rs6000: Remove some checks with aix[456]
Since
r12-75-g0745b6fa66c69c aix6 support had been dropped,
so we don't need to check for aix[456].* when testing, this
patch is to remove such checks.
gcc/testsuite/ChangeLog:
* lib/target-supports.exp
(check_effective_target_powerpc_altivec_ok): Remove checks for
aix[456].*
(check_effective_target_powerpc_p9modulo_ok): Likewise.
(check_effective_target_powerpc_float128_sw_ok): Likewise.
(check_effective_target_powerpc_float128_hw_ok): Likewise.
(check_effective_target_powerpc_vsx_ok): Likewise.