ml605_mmu: Move the hardcoded values to the init function

Move the hard coded register values to the init function.
This also allows the entire reset function to be deleted, as
PVR registers are now preserved on reset.

The hardcoded PVR0 values can be removed as they are setting
the endianness and stack protection, which is already done
or invalid.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>