Not all code that set or interpreted "mux_bits" was using the named
macros, but rather some was simply using hard-coded integer constants.
This makes it hard to determine which pieces of code are affected by
changes to those constants.

Replace the integer constants with the equivalent macro definitions so
that everything is nicely tied together.

Note that I'm not convinced all the code was using the correct integer
constants, and hence I'm not convinced that all the code is now using
the desired macros. However, this change is a purely mechanical
replacement and should have no functional change. Fixing any bugs will
come later, separately.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>