media: ddbridge/mci: split MaxSX8 specific code off to ddbridge-sx8.c

Split off all code specific to the MaxSX8 cards to a separate ddbridge-sx8
module and hook it up in the Makefile. This also adds evaluation of the
mci_type to allow for using different attach handling for different cards.
As different cards can implement things differently (ie. support differing
frontend_ops, and have different base structs being put ontop of the
common mci_base struct), this introduces the mci_cfg struct which is
initially used to hold a few specifics to the -sx8 submodule. While at it,
the handling of the i/q mode is adjusted slightly. Besides this and
handling mci_base and sx8_base struct pointers where needed, all code
is copied unmodified from ddbridge-mci.c.

Picked up from the upstream dddvb GIT.

Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>