ARM: dts: at91: sama5d2: Add missing flexcom definitions

Describe all the flexcom functions for all the flexcom nodes.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200514050301.147442-13-tudor.ambarus@microchip.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>