Cancel all relevant timers/works before suspending (wowlan).

This patch handles the following warning:
WARNING: at net/mac80211/util.c:565 queueing ieee80211 work while going to suspend
Backtrace:
[<bf07b598>] (ieee80211_can_queue_work+0x0/0x4c [mac80211])
[<bf07c28c>] (ieee80211_queue_work+0x0/0x30 [mac80211])
[<bf0690dc>] (ieee80211_sta_timer+0x0/0x3c [mac80211])
[<c00a3008>] (run_timer_softirq+0x0/0x220)
[<c009e530>] (__do_softirq+0x0/0x130)
[<c009e660>] (irq_exit+0x0/0xb4)
[<c004c4a0>] (ipi_timer+0x0/0x4c)
[<c0046350>] (do_local_timer+0x0/0x88)
[<c00488ec>] (cpu_idle+0x0/0xe0)
[<c05294e8>] (rest_init+0x0/0xe0)
[<c0008958>] (start_kernel+0x0/0x314)
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>