scsi: qla2xxx: Spinlock recursion in qla_target

The patch reverts changes done in qlt_schedule_sess_for_deletion() to
avoid spinlock recursion sess->vha->work_lock should be used instead
of ha->tgt.sess_lock, that can be locked in callers: qlt_reset() or
qlt_handle_login()

[mkp: roll in build warning reported by sfr]

Fixes: 1c6cacf4

 ("scsi: qla2xxx: Fixup locking for session deletion")
Cc: <stable@vger.kernel.org> #v4.17
Signed-off-by: Mikhail Malygin <m.malygin@yadro.com>
Reported-by: Mikhail Malygin <m.malygin@yadro.com>
Tested-by: Mikhail Malygin <m.malygin@yadro.com>
Acked-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>