[media] firedtv: add MAINTAINERS entry

There is currently discussion to add MAINTAINERS records for media
drivers that don't have one yet, possibly with 'orphan' or 'odd fixes'
status.  Here is a proper entry for the firedtv driver (for 1394
attached DVB STBs and 1394 attached DVB cards from Digital Everywhere).

The L: linux-media and T: linux-media.git lines in this entry are
redundant to what scripts/get_maintainer.pl would show automatically but
I added them for folks who read MAINTAINERS directly.  The "(firedtv)"
string is for those folks as well if they look for driver name rather
than file path.

The F: drivers/media/firewire/ pattern and the "FireWire media drivers"
title are currently synonymous with firedtv.  If more drivers get added
there, this can be revisited.

I don't have documentation or DVB-S2 devices to test, but I have DVB-C
and DVB-T devices for testing.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>