[MIPS] Make timer interrupt frequency configurable from kconfig.

Make HZ configurable.  DECSTATION can select 128/256/1024 HZ, JAZZ can
only select 100 HZ, others can select 100/128/250/256/1000/1024 HZ if
not explicitly specified).  Also remove all mach-xxx/param.h files and
update all defconfigs according to current HZ value.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>