nv50-: split tic format specification

nv50-: split tic format specification

We previously stored texture format information as it would appear in
the TIC.

We're about to support the new TIC layout that appeared with Maxwell,
so it makes more sense to store the data in a split-out format.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Acked-by: Ilia Mirkin <imirkin@alum.mit.edu>