drm/nv40: Try to set up CRE_LCD even if it has unknown bits set.

They don't seem to do anything useful, and we really want to program
CRE_LCD if we aren't lucky enough to find the right CRTC binding
already set.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>