i40iw: Do not free sqbuf when event is I40IW_TIMER_TYPE_CLOSE

When the event type is I40IW_TIMER_TYPE_CLOSE, there is no sqbuf and
it should not be freed as one in i40iw_schedule_cm_timer().

Fixes: f27b4746 ("i40iw: add connection management code")
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>