Add basic support for the Kontron KSwitch D10 MMT. It comes in two
variants: "6G-2GS" which features 6 Gigabit copper ports and two SFP
cages and "8G" which features 6 Gigbabit copper ports (where two are
2.5G capable).

For now the following is supported and working:
 - Kernel console
 - SFP cages
 - SPI
 - SGPIO
 - Watchdog
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Tested-by: Horatiu Vultur <horatiu.vultur@microchip.com>
[claudiu.beznea: fixed conflict on Makefile]
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220502224127.2604333-8-michael@walle.ccSigned-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>