drm/vkms: Drop vkms_connector_destroy() wrapper

This helper is just a wrapper that calls drm_connector_cleanup(), there's
no need to have another level of indirection.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406110235.3092055-2-javierm@redhat.com