[SCSI] ipr: Fix ipr PCI hotplug hang with CDROM attach

Currently, during PCI hotplug remove, if the upper layer
drivers of the attached devices send commands down as part
of the remove action, like a CDROM, the hotplug action
will hang forever due to the ipr driver returning
SCSI_MLQUEUE_HOST_BUSY. Patch fixes this.

Signed-off-by: Brian King <brking@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>