wil6210: abort P2P search when stopping P2P device

The nl80211 layer expects P2P search operation to be aborted
if needed when stopping P2P device. If the P2P search operation
is still running after returning from stop_p2p_device
it causes a WARN_ON and possibly a kernel crash.
Fix this by aborting the P2P search in wil_cfg80211_stop_p2p_device
and preventing P2P search from being started on a stopped P2P
device.
Note, the fix does not cover the case where a regular scan
is started on the P2P device. It will be completed in the
future when support is added for aborting a scan operation.

Signed-off-by: Lior David <qca_liord@qca.qualcomm.com>
Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>