qla2xxx: Prevent removal and board_disable race

Introduce mutual exclusion between the qla2xxx_remove_one PCI driver
callback and qla2x00_disable_board_on_pci_error, which is scheduled as
board_disable work by qla2x00_check_reg{32,16}_for_disconnect:

* Leave the driver-specific data attached to the underlying PCI device
intact in qla2x00_disable_board_on_pci_error, so that qla2x00_remove_one
has enough breadcrumbs to determine that any board_disable work has been
completed.

* In qla2xxx_remove_one, set a bit to prevent any subsequent
board_disable work from scheduling, then cancel and wait until pending
work has completed.

* Reuse the PCI device enable count check in qla2x00_remove_one to
determine if board_disable has occured. The original purpose of this
check was unnecessary since the driver remove function wasn't called
when the probe fails.

Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Acked-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/scsi/qla2xxx/qla_isr.c b/drivers/scsi/qla2xxx/qla_isr.c
index fd75b91..341c64d 100644
--- a/drivers/scsi/qla2xxx/qla_isr.c
+++ b/drivers/scsi/qla2xxx/qla_isr.c
@@ -117,7 +117,8 @@
 {
 	/* Check for PCI disconnection */
 	if (reg == 0xffffffff) {
-		if (!test_and_set_bit(PFLG_DISCONNECTED, &vha->pci_flags)) {
+		if (!test_and_set_bit(PFLG_DISCONNECTED, &vha->pci_flags) &&
+		    !test_bit(PFLG_DRIVER_REMOVING, &vha->pci_flags)) {
 			/*
 			 * Schedule this (only once) on the default system
 			 * workqueue so that all the adapter workqueues and the