board: fsl: lx2160ardb: add dts fixup function for RevC and newer

Since the new RevC LX2160A-RDB board has its 10G Aquantia PHYs at
different MDIO bus addresses, we must update both the kernel DTS and
u-boot's DTS (in case of DM_ETH) in case the board is indeed RevC or
newer. Use the newly introduced get_board_rev() function to trigger a
fixup of the kernel DTS to properly match the actual PHY addresses.
All this is encapsulated in the fdt_fixup_board_phy_revc() function
which will be used in the next patch.

Use the newly fdt_fixup_board_phy_revc() function introduced to
update both kernel's DTS and u-boot's DTS.

Signed-off-by: Florin Chiculita <florinlaurentiu.chiculita@nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>