R600: Reorganize lit tests and document how they should be organized

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179828 91177308-0d34-0410-b5e6-96231b3b80d8
R600/SI: Use InstFlag for VOP3 modifier operands

InstFlag has a default value of 0 and will simplify the VOP3 patterns.

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179829 91177308-0d34-0410-b5e6-96231b3b80d8
R600: Add pattern for the BFI_INT instruction

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179830 91177308-0d34-0410-b5e6-96231b3b80d8