[MIPS] Show actual CPU information in /proc/cpuinfo

Currently, /proc/cpuinfo contains several copies of the information for
whatever processor we happen to be scheduled on. This patch makes it contain
the proper information for each CPU, which is particularly useful on mixed
R12k/R10k IP27 machines.

Signed-off-by: Karl-Johan Karlsson <creideiki@lysator.liu.se>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>