configs: sama7g5ek: enable mii command

Enable mii command as ethernet's PHY specific programming is
based on it.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
diff --git a/configs/sama7g5ek_mmc1_defconfig b/configs/sama7g5ek_mmc1_defconfig
index 99e2439..176f4f3 100644
--- a/configs/sama7g5ek_mmc1_defconfig
+++ b/configs/sama7g5ek_mmc1_defconfig
@@ -29,6 +29,7 @@
 # CONFIG_CMD_LOADS is not set
 CONFIG_CMD_MMC=y
 CONFIG_CMD_DHCP=y
+CONFIG_CMD_MII=y
 CONFIG_CMD_PING=y
 CONFIG_CMD_EXT4=y
 CONFIG_CMD_FAT=y