scsi: mpt3sas: Remove in_interrupt()

_scsih_fw_event_cleanup_queue() waits for all outstanding firmware events
wokrqueue handlers to finish. If in_interrupt() is true, it cancels itself
and return early.

That in_interrupt() check is ill-defined and does not provide what the name
suggests: it does not cover all states in which it is safe to block and
call functions like cancel_work_sync().

That check is also not needed: _scsih_fw_event_cleanup_queue() is always
invoked from process context. Below is an analysis of its callers:

  - scsih_remove(), bound to PCI ->remove(), process context

  - scsih_shutdown(), bound to PCI ->shutdown(), process context

  - mpt3sas_scsih_clear_outstanding_scsi_tm_commands(), called by
      => _base_clear_outstanding_commands(), called by
        =>_base_fault_reset_work(), workqueue
        => mpt3sas_base_hard_reset_handler(), locks mutex

Remove the in_interrupt() check. Change _scsih_fw_event_cleanup_queue()
specification to a purely process-context function and mark it with
"Context: task, can sleep".

Link: https://lore.kernel.org/r/20201126132952.2287996-10-bigeasy@linutronix.de
Cc: Sathya Prakash <sathya.prakash@broadcom.com>
Cc: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Cc: Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>
Cc: <MPT-FusionLinux.pdl@broadcom.com>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/mpt3sas/mpt3sas_scsih.c

@@ -3673,6 +3673,8 @@ static struct fw_event_work *dequeue_next_fw_event(struct MPT3SAS_ADAPTER *ioc)
  *
  * Walk the firmware event queue, either killing timers, or waiting
  * for outstanding events to complete
+ *
+ * Context: task, can sleep
  */
 static void
 _scsih_fw_event_cleanup_queue(struct MPT3SAS_ADAPTER *ioc)
@@ -3680,7 +3682,7 @@ _scsih_fw_event_cleanup_queue(struct MPT3SAS_ADAPTER *ioc)
 	struct fw_event_work *fw_event;
 
 	if ((list_empty(&ioc->fw_event_list) && !ioc->current_event) ||
-	     !ioc->firmware_event_thread || in_interrupt())
+	    !ioc->firmware_event_thread)
 		return;
 
 	ioc->fw_events_cleanup = 1;