[RS6000] Power10 libffi fixes
Power10 pc-relative code doesn't use or preserve r2 as a TOC pointer.
That means calling between pc-relative and TOC using code can't be
done without intervening linker stubs, and a call from TOC code to
pc-relative code must have a nop after the bl in order to restore r2.
Now the PowerPC libffi assembly code doesn't use r2 except for the
implicit use when making calls back to C, ffi_closure_helper_LINUX64
and ffi_prep_args64. So changing the assembly to interoperate with
pc-relative code without stubs is easily done.
PR target/97166
* src/powerpc/linux64.S (ffi_call_LINUX64): Don't emit global
entry when __PCREL__. Call using @notoc. Add nops.
* src/powerpc/linux64_closure.S (ffi_closure_LINUX64): Likewise.
(ffi_go_closure_linux64): Likewise.
(cherry picked from commit
08cd8d5929eac84b27788d8483fd75ab7ad13129)
(cherry picked from commit
fff56af6421a1a3e357bcaad99f2ea084d72a7a8)