R4K-style CPUs having common code to support their caches and tlb have this
boolean defined by default. Allows us to remove some lines in
arch/mips/mm/Makefile.
Signed-off-by: NFlorian Fainelli <florian@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/3328/Signed-off-by: NJohn Crispin <blogic@openwrt.org>