ARM: at91/dt: sama5d2 Xplained: add several devices

Add sdmmc and flexcom devices

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>