R600: Code cleanup.

Use sign_extend_inreg and getZeroExtendInReg instead of
using the bit operations they expand into.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203988 91177308-0d34-0410-b5e6-96231b3b80d8
R600: Remove unnecessary attempt to zext a pointer.

Private pointers are now always 32-bits.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203989 91177308-0d34-0410-b5e6-96231b3b80d8