Minor constant cleanup

Minor constant cleanup

In order to make the code a bit more readable and a little
less error prone, constants that are the bitwise inverted
version of other constants are computed from those constants
rather than being recomputed from scratch.

Change-Id: I27759d23e9c72b683eeafe4583b76a62e8132f19
Reviewed-on: https://swiftshader-review.googlesource.com/5590
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>