[MIPS] tlbex: use __maybe_unused

Replace function instances of __attribute__((unused)) with
__maybe_unused.

Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --cc arch/mips/mm/tlbex.c
Simple merge