Restore Xmm registers properly in StgCRun.c
Restore Xmm registers properly in StgCRun.c

This fixes #16514: Xmm6-15 was restored based off rax instead of rsp.
The code was introduced in the fix for #14619.

sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc