[media] media: v4l2-dev.h: remove V4L2_FL_USE_FH_PRIO flag

Since none of the drivers are using it, this flag can be removed.

Signed-off-by: Ramakrishnan Muthukrishnan <ramakrmu@cisco.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>