R600: Fix segfault in R600TextureIntrinsicReplacer

This pass was segfaulting when it ran into a non-intrinsic function
call.  Function calls are not supported, so now instead of segfaulting,
we will get an assertion failure with a nice error message.

I'm not sure how to test this using lit.
R600/SI: Don't emit S_WQM_B64 instruction for compute shaders
R600: Fix incorrect LDS size calculation

GlobalAdderss nodes that appeared in more than one basic block were
being counted twice.
R600: Expand SELECT nodes rather than custom lowering them
R600: Add support for local memory atomic add