net: macb: Fix build error for CONFIG_DM_ETH enabled

Use the right phy_connect() prototype for CONFIGF_DM_ETH.
Support to get the phy interface from dt and set GMAC_UR.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>