[PowerPC] Promote the i1 to i64 for SINT_TO_FP/FP_TO_SINT

i1 is the native type for PowerPC if crbits is enabled. However, we need
to promote the i1 to i64 as we didn't have the pattern for i1.

Reviewed By: Qiu Chao Fang

Differential Revision: https://reviews.llvm.org/D92067