Passes all texelFetch and texelFetchOffset tests in dEQP.

Change-Id: Ic212d326d1c062f1947696e6963fef300b7737f1
Reviewed-on: https://swiftshader-review.googlesource.com/5512Tested-by: Meng-Lin Wu <marleymoo@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>