[ARM] Expand the range of allowed post-incs in load/store optimizer

Currently the load/store optimizer will only fold in increments of the
same size as the load/store. This patch expands that to any legal
immediate for the post-inc instruction.

Differential Revision: https://reviews.llvm.org/D95885

GitOrigin-RevId: 3b34b06fc5908b4f7dc720c0655d5756bd8e2a28
4 files changed