ARM: mxs/mx28evk: read fec mac address from ocotp

Read fec mac address from ocotp and save it into fec_platform_data
mac field for fec driver to use.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>