ARM: at91: at91sam9m10g45ek/dt: add leds support

Use the gpio for d7 as we do not support yet the pwm led via dt.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>