drm/cirrus: Store HW format/pitch in primary-plane state

The hardware settings for color format and pitch are state of the
primary plane. Store the values in the primary plane's state structure
struct cirrus_primary_plane_state. Adapt all callers.

All fields in struct cirrus_device are now considered immutable after
initialization. Plane updates consider the difference between the old
and the new plane state before updating format or pitch.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230215161517.5113-17-tzimmermann@suse.de