When suspending, __ieee80211_suspend() calls ieee80211_scan_cancel(),
which will only cancel sw scan. In order to cancel hw scan, the
low-level driver has to cancel it in the suspend() callback. however,
this is too late, as a new scan_work will be enqueued (while the driver
is going into suspend).

Add a new cancel_hw_scan() callback, asking the driver to cancel an
active hw scan, and call it in ieee80211_scan_cancel().
Signed-off-by: NEliad Peller <eliad@wizery.com>
Reviewed-by: NStanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>