R600/SI: Emit config values in register value pairs.

Instead of emitting config values in a predefined order, the code
emitter will now emit a 32-bit register index followed by the 32-bit
config value.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179546 91177308-0d34-0410-b5e6-96231b3b80d8