[AArch64][GlobalISel] Legalize narrow scalar fp->int conversions.

Since we're now avoiding operations using narrow scalar integer types,
we have to legalize the integer side of the FP conversions.

This requires teaching the legalizer how to do that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292828 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed