[MIPS] SNI RM updates

- use RTC_CLASS instead of GEN_RTC
- get rid of ds1216 in favour of a RTC_CLASS driver
- use correct console device for older RM400
- use physical addresses for 82596 device
- use 128 byte L1 cache line size (this is needed because most of the
  SNI caches are using 128 L2 cache lines)

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