configs: ls1046afrwy: enable DM_MDIO and DM_CMD

With DM_ETH configured by default, complete the Ethernet enablement for
LS1046AFRWY by activating DM_MDIO.

Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>