net: fec_mxc: fix PHY initialization bug with CONFIG_DM_ETH

When CONFIG_DM_ETH is set, the FEC ethernet controller is reset after
the PHY has been set up and initialzed. This breaks the communication
with the PHY and results in an inoperable ethernet interface.

Do the initialization with CONFIG_DM_ETH in the same order as with
legacy ETH support to fix this.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>