fb: fix colliding defines for fb flags.

When I added the flags I must have been using a 25 line terminal and missed the following flags.

The collided with flag has one user in staging despite being in-tree for 5 years.

I'm happy to push this via my drm tree unless someone really wants to do it.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Cc: stable@kernel.org