cciss: do not use bit 2 doorbell reset

It causes NMIs which are undesirable at best, unsurvivable at worst.
Prefer the soft reset instead.

Signed-off-by: Stephen M. Cameron <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/block/cciss.c

···
 		use_doorbell = DOORBELL_CTLR_RESET2;
 	} else {
 		use_doorbell = misc_fw_support & MISC_FW_DOORBELL_RESET;
-		if (use_doorbell)
-			use_doorbell = DOORBELL_CTLR_RESET;
+		if (use_doorbell) {
+			dev_warn(&pdev->dev, "Controller claims that "
+				"'Bit 2 doorbell reset' is "
+				"supported, but not 'bit 5 doorbell reset'.  "
+				"Firmware update is recommended.\n");
+			rc = -ENOTSUPP; /* use the soft reset */
+			goto unmap_cfgtable;
+		}
 	}
 
 	rc = cciss_controller_hard_reset(pdev, vaddr, use_doorbell);