[MIPS] Add Missing R4K Cache Macros to IP27 & IP32

Keeping in accordance with other machines, IP27 and IP32 lack a few
macros.  IP27 lacks cpu_has_4kex & cpu_has_4k_cache macros while IP32
lacks just the cpu_has_4k_cache macro.

Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>