[media] drxd: provide ability to control rs byte

Provide the ability for the board configuration to specify whether to insert
the RS byte into the TS interconnect to the bridge, while not required for
the ngene in fact is required for the em28xx.

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>