ARM: at91/dt: sama5d4 xplained: add regulators for v(q)mmc1 supplies

Add vcc_mmc1 fixed regulator to remove the 'no vmmc regulator found' warning
when probing the mmc1 device.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>