R600: Simplify stream outputs intrinsic

Patch by: Vincent Lejeune

Reviewed-by: Tom Stellard <thomas.stellard@amd.com>
R600: Add a llvm.R600.store.swizzle intrinsics

This intrinsic is translated to ALLOC_EXPORT_WORD1_SWIZ, hence its
name. It is used to store vs/fs outputs

Patch by: Vincent Lejeune

Reviewed-by: Tom Stellard <thomas.stellard@amd.com>