[SERIAL] dz: Use CKSEG1ADDR to setup mappings.

Use physical addresses at the interface level, letting drivers remap
them as appropriate.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>