ARM: at91/defconfig: add DM9000 to at91_dt

This chip is present on at91sam9261ek board: add it to the at91_dt_defconfig.
Signed-off-by: NNicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/configs/at91_dt_defconfig

@@ -80,6 +80,7 @@ CONFIG_BLK_DEV_SD=y
 CONFIG_NETDEVICES=y
 CONFIG_MACB=y
 # CONFIG_NET_VENDOR_BROADCOM is not set
+CONFIG_DM9000=y
 # CONFIG_NET_VENDOR_FARADAY is not set
 # CONFIG_NET_VENDOR_INTEL is not set
 # CONFIG_NET_VENDOR_MARVELL is not set