[media] cec: don't Feature Abort broadcast msgs when unregistered

If the adapter is configured as 'Unregistered', then cec_receive_notify
incorrectly thinks that broadcast messages are directed messages. The
destination for broadcast messages is 0xf, and the logical address
assigned to Unregistered devices is also 0xf and the logic didn't handle
that correctly.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>