[AArch64][GlobalISel] Zero-extend s1 values when returning.

Before we were relying on the any extend of the s1 to s32, but
for AAPCS we need to zero-extend it to at least s8.

Fixes PR36719

Differential Revision: https://reviews.llvm.org/D47425

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@333747 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed