From: Tao Ren <rentao.bupt@xxxxxxxxx>
Enable mac3 controller in Elbert dts: Elbert MAC3 is connected to the
BCM53134P onboard switch's IMP_RGMII port directly (fixed link, no PHY
between BMC MAC and BCM53134P).
Note: BMC's mdio0 controller is connected to BCM53134P's MDIO interface,
and the MDIO channel will be enabled later, when BCM53134 is added to
"bcm53xx" DSA driver.
Signed-off-by: Tao Ren <rentao.bupt@xxxxxxxxx>