net/fman: add ft_fixup_xgec to support 3rd and 4th 10GEC

As mEMAC1 and mEMAC2 are dual-role MACs, which are used as 1G or 10G MAC.
So we update dynamically 'cell-index' to '2' and '3' for 10GEC3 and 10GEC4.
Also change 'fsl,fman-port-1g-rx' to 'fsl,fman-port-10g-rx', ditto for Tx.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
Acked-by: York Sun <yorksun@freescale.com>