drm/vc4: hvs: Align the HVS atomic hooks to the new API

Since the CRTC setup in vc4 is split between the PixelValves/TXP and the
HVS, only the PV/TXP atomic hooks were updated in the previous commits, but
it makes sense to update the HVS ones too.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215154243.540115-2-maxime@cerno.tech