[AArch64][GlobalISel] Don't do extending loads combine for non-pow-2 types.

Since non-pow-2 types are going to get split up into multiple loads anyway,
don't do the [SZ]EXTLOAD combine for those and save us trouble later in
legalization.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358458 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed