[MIPS] Unify dump_tlb

Unify lib-{32,64}/dump_tlb.c into lib/dump_tlb.c and move
lib-32/r3k_dump_tlb.c to lib directory.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>