MLK-9694 ARM: imx6: init enet MAC address

MLK-9694 ARM: imx6: init enet MAC address

Enet get MAC address order:
From module parameters or kernel command line -> device tree ->
pfuse -> mac registers set by bootloader -> random mac address.

When there have no "fec.macaddr" parameters set in kernel command
line, enet driver get MAC address from device tree. And then if
the MAC address set in device tree and is valid, enet driver get
MAC address from device tree. Otherwise,enet get MAarch/arm/mach-imx
/mach-imx6q.cC address from
pfuse. So, in the condition, update the MAC address (read from pfuse)
to device tree.

Cherry-pick & Merge patches from:
149ac988a25b8d8eb86d05679cbb7b42819ff7a1 &
3269e5c06bdb2f7ab9bd5afa9bbfe46d872197d3

Signed-off-by: Fugang Duan <B38611@freescale.com>