ARM: dts: at91: sama5d2: Move flx3 definitions in the SoC dtsi

The Flexcom IP is part of the sama5d2 SoC. Move the flx3 node together
with its function definitions in sama5d2.dtsi. Boards will just fill
the pins and enable the desired functions.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200514050301.147442-4-tudor.ambarus@microchip.com


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