MIPS: introduce CPU_GENERIC_DUMP_TLB

Allows us not to duplicate more lines in arch/mips/lib/Makefile.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/3329/


Signed-off-by: John Crispin <blogic@openwrt.org>