nv50,nvc0: enable TEX_LZ and TXF_LZ

nv50,nvc0: enable TEX_LZ and TXF_LZ

There should be minimal gain, if any, for nvc0, but nv50 may end up
noticing more often that the lod argument is uniform. This, in turn,
will remove the need for some unnecessary transformations, which were
being hit due to the checks being done pre-ssa.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>