ARM: at91/at91_dt_defconfig: add at91sam9n12 SoC to DT defconfig

Reported-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/configs/at91_dt_defconfig

@@ -19,6 +19,7 @@ CONFIG_SOC_AT91SAM9260=y
 CONFIG_SOC_AT91SAM9263=y
 CONFIG_SOC_AT91SAM9G45=y
 CONFIG_SOC_AT91SAM9X5=y
+CONFIG_SOC_AT91SAM9N12=y
 CONFIG_MACH_AT91SAM_DT=y
 CONFIG_AT91_PROGRAMMABLE_CLOCKS=y
 CONFIG_AT91_TIMER_HZ=128