Remove the option, because it is hard to use.
Drm connector ids are hard to reach for users,
and they can change when kernel or device tree
is modified.

Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
[Pekka: bump WESTON_DRM_BACKEND_CONFIG_VERSION]
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>