media: ddbridge: initial support for MCI-based MaxSX8 cards

This adds initial support for the new MCI-based (micro-code interface)
DD cards, with the first one being the MaxSX8 eight-tuner DVB-S/S2/S2X
PCIe card. The MCI is basically a generalized interface implemented in
the card's FPGA firmware and usable for all kind of cards, without the
need to implement any demod/tuner drivers as this interface "hides" any
I2C interface to the actual ICs, in other words any required driver is
implemented in the card firmware.

At this stage, the MCI interface is quite rudimentary with things like
signal statistics reporting missing, but is already working to serve
DVB streams to DVB applications. Missing functionality will be enabled
over time.

This implements only the ddbridge-mci sub-object and hooks it up to the
Makefile so the object gets build. The upcoming commits hook this module
into all other ddbridge parts where required, including device IDs etc.

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>