scsi: qla2xxx: Unregister chrdev if module initialization fails

If module initialization fails after the character device has been
registered, unregister the character device. Additionally, avoid
duplicating error path code.

Cc: Himanshu Madhani <hmadhani@marvell.com>
Cc: Giridhar Malavali <giridhar.malavali@qlogic.com>
Fixes: 6a03b4cd ("[SCSI] qla2xxx: Add char device to increase driver use count") # v2.6.35.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>