media: ddbridge/mci: extend mci_command and mci_result structs

Recent FPGA firmware reports more data and values in sent command
responses. Adjust the mci_command and mci_result structs including it's
unions to match these changes and add a few comments explaining things.

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>