Packing fix Unified and fixed packing and unpacking computations. Change-Id: I1ea2bcf28945a9f105152a6836f11bcb2859750c Reviewed-on: https://swiftshader-review.googlesource.com/4715 Tested-by: Alexis Hétu <sugoi@google.com> Reviewed-by: Nicolas Capens <capn@google.com>