ar71xx: Add net config for MR12 & MR16

Both the MR12 and MR16 are single gigabit ethernet devices, similar to the
MR18. This change gives them the correct network config on a fresh install.

Signed-off-by: Chris Blake <chrisrblake93@gmail.com>
[Jo-Philipp Wich: adjust for alphabetical ordering, line wrap commit msg]
Signed-off-by: Jo-Philipp Wich <jo@mein.io>

target/linux/ar71xx/base-files/etc/board.d/02_network

@@ -71,6 +71,8 @@ ar71xx_setup_interfaces()
 	eap7660d|\
 	el-mini|\
 	loco-m-xw|\
+	mr12|\
+	mr16|\
 	mr1750|\
 	mr1750v2|\
 	mr18|\