drm/meson: Use crtc_state for hdisplay and fix atomic flush/enable sync for vsync commit

Clean the crtc_enable by using the proper crtc_state instead of the state
of the primary plane state data.

Also fix the dependency to commit the plane changes even if enable is called
after the flush.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>