IB/hfi1: Insure freeze_work work_struct is canceled on shutdown

By code inspection, the freeze_work is never canceled.

Fix by adding a cancel_work_sync in the shutdown path to insure it is no
longer running.

Fixes: 7724105686 ("IB/hfi1: add driver files")
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/hfi1/chip.c

@@ -9850,6 +9850,7 @@ void hfi1_quiet_serdes(struct hfi1_pportdata *ppd)
 
 	/* disable the port */
 	clear_rcvctrl(dd, RCV_CTRL_RCV_PORT_ENABLE_SMASK);
+	cancel_work_sync(&ppd->freeze_work);
 }
 
 static inline int init_cpu_counters(struct hfi1_devdata *dd)