To share the same kernel image amon different machines we have added the
machtype command line support.

In the old serial port implementation the UART base address is hardcoded as
a macro in machine.h which breaks with machtype, so change that to discover
the address dynamically.  Also move the initialization of the UART base
address to uart_base.c to avoid remapping twice for early_printk.c and
serial.c.
Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/581/
Patchwork: http://patchwork.linux-mips.org/patch/682/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>