[MIPS] RM: Collected changes

- EISA support for non PCI RMs (RM200 and RM400-xxx). The major part
  is the splitting of the EISA and onboard ISA of the RM200, which
  makes the EISA bus on the RM200 look like on other RMs.
- 64bit kernel support
- system type detection is now common for big and little endian
- moved sniprom code to arch/mips/fw
- added call_o32 function to arch/mips/fw/lib, which uses a private
  stack for calling prom functions
- fix problem with ISA interrupts, which makes using PIT clockevent
  possible

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>