Revert "s390/pci: remove bit_lock usage in interrupt handler"

This reverts commit 9594ca6b87d9f11e9f14ac31581e0e5d79a8e839.

With the handle_simple_irq irq_flow_handler it must be ensured to
not call generic_handle_irq with the same IRQ number on 2 CPUs at
the same time (interrupts are floating on s390).
Contrary to my initial investigation the irq_desc's lock usage in
handle_simple_irq does not ensure this. Thus re-introduce the bit-
lock usage in s390's pci handler.

Reported-by: Ursula Braun <[e-mail]>
Reported-by: Alexander Schmidt <[e-mail]>
Signed-off-by: Sebastian Ott <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/pci/pci.c

···
 			if (ai == -1UL)
 				break;
 			inc_irq_stat(IRQIO_MSI);
+			airq_iv_lock(aibv, ai);
 			generic_handle_irq(airq_iv_get_data(aibv, ai));
+			airq_iv_unlock(aibv, ai);
 		}
 	}
 }
···
 	zdev->aisb = aisb;
 
 	/* Create adapter interrupt vector */
-	zdev->aibv = airq_iv_create(msi_vecs, AIRQ_IV_DATA);
+	zdev->aibv = airq_iv_create(msi_vecs, AIRQ_IV_DATA | AIRQ_IV_BITLOCK);
 	if (!zdev->aibv)
 		return -ENOMEM;