[ARM|CodeGen] Improve the code in FastISel

Cleaned up the code in FastISel a bit.
Had to add make_range to MCInstrDesc as that was needed and seems missing.

Reviewed by: @t.p.northover
Differential Revision: https://reviews.llvm.org/D35494



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@308291 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed