MIPS: Fix decoding of c0_config1 for MIPSxx caches with 32 ways per set.

This affects certain 4Kc cores.

Signed-off-by: Douglas Leung <douglas@mips.com>
Signed-off-by: Steven J. Hill <sjhill@mips.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3855/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>