mpc85xx: Configure QE UART for MPC8569E-MDS boards

To make QE UART usable by Linux we should setup pin multiplexing
and turn UCC2 Ethernet node into UCC2 QE UART node.

Also, QE UART is mutually exclusive with UART0, so we can't enable
it if eSDHC is in 4-bits mode on pilot boards, or if it's a prototype
board with eSDHC in 1- or 4-bits mode.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>