media: add flags field to struct media_v2_entity

The v2 entity structure never exposed the entity flags, which made it
impossible to detect connector or default entities.

It is really trivial to just expose this information, so implement this.

Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>