V4L/DVB (13237): firedtv: length field corrupt in ca2host if length>127

This solves a problem in firedtv that has become major for Swedish DVB-T
users the last month or so.  It will most likely solve issues seen by
other users as well.

If the length of an AVC message is greater than 127, the length field
should be encoded in LV mode instead of V mode. V mode can only be used
if the length is 127 or less. This patch ensures that the CA_PMT
message is always encoded in LV mode so PMT message of greater lengths
can be supported.

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