[Bug go/66870] split stack issues on ppc64le and ppc64

[boger at us dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66870

--- Comment #28 from boger at us dot ibm.com ---
I could put back the #ifdef TARGET_CAN_SPLIT_STACK_64BIT around the OPT_m32
case if that is OK.

Doesn't fail on the builds for ppc64le or ppc64 either.