ARM: dts: at91: sama5d2_xplained: Describe the flx0 I2C function

ARM: dts: at91: sama5d2_xplained: Describe the flx0 I2C function

Users can choose which flexcom function to use. Describe the I2C
Flexcom0 function. Add alias for the i2c2 node in order to not rely
on probe order for the i2c device numbering. The sama5d2 SoC has
two dedicated i2c buses and five flexcoms that can function as i2c.
The i2c0 and i2c1 aliases are kept for the dedicated i2c buses,
the i2c flexcom functions can be numbered in order starting from i2c2.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200514050301.147442-16-tudor.ambarus@microchip.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>