[PowerPC] Fix SH field overflow issue

Store rlwinm Rx, Ry, 32, 0, 31 as rlwinm Rx, Ry, 0, 0, 31 and store
rldicl Rx, Ry, 64, 0 as rldicl Rx, Ry, 0, 0. Otherwise SH field is overflow and
fails assertion in assembly printing stage.

Differential Revision: https://reviews.llvm.org/D66991

llvm-svn: 373519