MIPS: Add hibernation support

[Ralf: SMP support requires CPU hotplugging which MIPS currently doesn't
support.  As implemented in this patch cache and tlb flushing will also be
invoked with interrupts disabled so smp_call_function() will blow up in
charming ways.  So limit to !SMP.]

Reviewed-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Yan Hua <yanh@lemote.com>
Reviewed-by: Arnaud Patard <apatard@mandriva.com>
Reviewed-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Wu Zhangjin <wuzj@lemote.com>
Signed-off-by: Hu Hongbing <huhb@lemote.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>