drm/gma500: gma500 don't register non-hotpluggable connectors

According to docs we should only register connectors that are
hotpluggable. No connectors in gma500 are hotpluggable.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220322131742.11566-4-patrik.r.jakobsson@gmail.com