ARM: dts: at91: sama5d27_som1_ek: add aliases for i2c

Add aliases for i2c devices to not rely on probe order for i2c device
numbering.

Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>
[claudiu.beznea@microchip.com: remove i2c0, change subject]
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>