mips: select ARCH_MIGHT_HAVE_PC_SERIO

Architectures which might use an i8042 for serial IO to keyboard,
mouse, etc should select ARCH_MIGHT_HAVE_PC_SERIO.

Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
CC: linux-mips@linux-mips.org
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6232/