[media] firedtv: add parameter to fake ca_system_ids in CA_INFO

The Digital Everywhere firmware have the shortcoming that ca_info_enq and
ca_info are not supported. This means that we can never retrieve the correct
ca_system_id to present in the CI message CA_INFO. Currently the driver uses
the application id retrieved using app_info_req and app_info, but this id
only match the correct ca_system_id as given in ca_info in some cases.
This patch adds a parameter to the driver in order for the user to override
what will be returned in the CA_INFO CI message. Up to four ca_system_ids can
be specified.
This is needed for users with CAMs that have different manufacturer id and
ca_system_id and that uses applications that take this into account, like
MythTV.

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>