After https://go-review.googlesource.com/c/36725/, ppc64x no longer
needs a temp stack location for int reg <-> fp reg moves.

Update #18922

Change-Id: Ib4319784f7a855f593dfa5231604ca2c24e4c882
Reviewed-on: https://go-review.googlesource.com/37651Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>