drm/nouveau: fix booting with plymouth + dumb support

commit 610bd7da160f76f1644ecb4cd7f39511b49a22cc upstream.

We noticed a plymouth bug on Fedora 18, and I then
noticed this stupid thinko, fixing it fixed the problem
with plymouth.

Acked-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>