scsi: qla2xxx: Fix a locking imbalance in qlt_24xx_handle_els()

Ensure that upon return the tgt->ha->tgt.sess_lock spin lock is unlocked
no matter which code path is taken through this function.  This was
detected by sparse.

Fixes: 82abdcaf

 ("scsi: qla2xxx: Allow target mode to accept PRLI in dual mode")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Himanshu Madhani <himanshu.madhani@cavium.com>
Cc: Quinn Tran <quinn.tran@cavium.com>
Acked-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>