armv8: ls1088a: Update MC boot sequence

The MC boot sequence is contained in mc_env_boot. Update LS1088A
boards to use this function, and hook it to reset_phy so that it's
called late enough, after the ports have been initialized, for
proper DPC / DPL fixup.

Signed-off-by: Bogdan Purcareata <bogdan.purcareata@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>