media: ddbridge/max: implement MCI/MaxSX8 attach function

Implement frontend attachment as ddb_fe_attach_mci() into the
ddbridge-max module. The MaxSX8 MCI cards are part of the Max card series
and make use of the LNB controller driven by the already existing lnb
functionality, so here's where this code belongs to.

Picked up from the upstream dddvb-0.9.33 release.

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