AMDGPU/SI: Don't set DATA_FORMAT if ADD_TID_ENABLE is set

to prevent setting a huge stride, because DATA_FORMAT has a different
meaning if ADD_TID_ENABLE is set.

This is a candidate for stable llvm 3.7.

Tested-and-Reviewed-by: Christian König <christian.koenig@amd.com>
llvm-svn: 248858