drm/ast: Enable primary plane with CRTC

As the CRTC requires a primary plane for display, ensure that the
primary plane is enabled with the CRTC.

Use drm_atomic_helper_check_crtc_state(). Add all affected planes
to the atomic state so that their state will be checked as well.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220617103226.25617-4-tzimmermann@suse.de