arm64: dts: ls1043a-qds: add mmio based mdio-mux support

There is mmio based mdio mux function in the FPGA device on ls1043a-qds
board.  Add the mmio based mdio-mux nodes to ls1043a-qds boards and
add simple-mfd as a compatbile for the FPGA node to reflect the
multi-function nature of it.  Also connect the ethernet interfaces to
these phy interfaces.

Signed-off-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>