[Bug target/80123] libgomp tests pr66199-2.c and pr66199-5.c fail with -mcpu=power9

[acsawdey at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80123

--- Comment #1 from acsawdey at gcc dot gnu.org ---
Changing the final constraint of vsx_splat_<mode> from "wr" to "b" allows this
to compile and pass the execution test. 

This isn't really a correct fix as "b" is not NO_REGS if 64-bit instructions
are disabled.

;; V2DF/V2DI splat
(define_insn_and_split "vsx_splat_<mode>"
  [(set (match_operand:VSX_D 0 "vsx_register_operand"
                                        "=<VSa>,    <VSa>,we,<VS_64dm>")
        (vec_duplicate:VSX_D
         (match_operand:<VS_scalar> 1 "splat_input_operand"
                                        "<VS_64reg>,Z,    b, wr")))]