MIPS: Alchemy: Merge PB1200 support into DB1200 code.

The PB1200 is basically a DB1200 with additional MMC and camera sockets
and different base addresses for external hardware (CPLD, IDE, Net, NAND).

This patch implements the missing PB1200 features in DB1200 support code
and runtime board detection.

Tested on DB1200 only.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2880/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>