arm64: defconfig: enable MVNETA

Now that the Armada 37xx SoCs support the mvneta driver, enable it by
default. It is especially useful when booting on an NFS root.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm64/configs/defconfig

@@ -185,6 +185,7 @@ CONFIG_HNS_ENET=y
 CONFIG_E1000E=y
 CONFIG_IGB=y
 CONFIG_IGBVF=y
+CONFIG_MVNETA=y
 CONFIG_SKY2=y
 CONFIG_RAVB=y
 CONFIG_SMC91X=y