i965/dri: Enable modifier queries

i965/dri: Enable modifier queries

New to the patch series after reordering things for landing smaller
chunks.

This will essentially enable modifiers from clients that were just
enabled in previous patches. A client could use the modifiers by
setting all of them at create, but had no way to actually query them
after creating the surface (ie. stupid clients could be broken before
this patch, but in more ways than this).

Obviously, there are no modifiers being actually stored yet - so this
patch shouldn't do anything other than allow the API to get back 0 (or
the LINEAR modifier).

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>