powerpc/p2041: move Lanes mux to board early init

Lanes mux currently is configured in eth.c when initializing FMAN ethernet
ports, but SRIO and PCIe also need lanes mux, so we move the lanes mux to
p2041rdb.c which implements a board-specific initialization and will be
called at early stage.

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>