[PowerPC] Use subfic instruction for subtract from immediate

Provide a 64-bit pattern to use SUBFIC for subtracting from a 16-bit immediate.
The corresponding pattern already exists for 32-bit integers.

Committing on behalf of Hiroshi Inoue.

Differential Revision: https://reviews.llvm.org/D29387


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296144 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed