ARM: at91/defconfig: add at91rm9200 ethernet support

There is now only one defconfig for the at91rm9200 and at91sam9. Add ethernet
support for the at91rm9200.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/configs/at91_dt_defconfig

@@ -70,6 +70,7 @@ CONFIG_SCSI=y
 CONFIG_BLK_DEV_SD=y
 # CONFIG_SCSI_LOWLEVEL is not set
 CONFIG_NETDEVICES=y
+CONFIG_ARM_AT91_ETHER=y
 CONFIG_MACB=y
 # CONFIG_NET_VENDOR_BROADCOM is not set
 CONFIG_DM9000=y