drm/vc4: Bind the HVS before we bind the individual CRTCs.

We need to be able to look at the CRTC's registers in the HVS as part
of initialization, while the HVS doesn't need to look at the PV
registers.

Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-and-tested-by: Mario Kleiner <mario.kleiner.de@gmail.com>