drm/vc4: kms: Move clock request to our HVS state

Our current clock request has been stored so far on the main HVS
structure, but even though we shouldn't have two commits in parallel and
it shouldn't cause any functional change, the request itself is linked
to a given HVS state.

Move the request there to make a bit more sense.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>