R600/SI: Store immediate offsets > 12-bits in soffset

This will save us from having to extend these offsets to 64-bits
and storing them in a pair of vgprs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228776 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed