powerpc/ppc4xx: Do full iocon PHY initialization in software

Up to this point some PHY initialization was done from the FPGA
and some from u-boot.
From now all initialization is done from u-boot.
To keep this maintainable a PHY setup machine was implemented that can
execute commands from initialization arrays.

Signed-off-by: Dirk Eibach <dirk.eibach@gdsys.cc>
Signed-off-by: Stefan Roese <sr@denx.de>