bcmdhd: Clear dhd driver hang event

bcmdhd: Clear dhd driver hang event

Clear dhd driver hang event upon device close, so that next open
will not be blocked.

Prevents condition where wifi cannot be turned off / on because
of a previous hang event flag being set.

Bug 1280309

Change-Id: I6569cd39c8866682c7a19fa840b32162c2a4dd5b
Signed-off-by: Michael Hsu <mhsu@nvidia.com>
Reviewed-on: http://git-master/r/229999
Reviewed-by: Rakesh Kumar <krakesh@nvidia.com>
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Matt Wagner <mwagner@nvidia.com>
GVS: Gerrit_Virtual_Submit