scsi: target: core: Fix warning on RT kernels

Calling spin_lock_irqsave() does not disable the interrupts on realtime
kernels, remove the warning and replace assert_spin_locked() with
lockdep_assert_held().

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230110125310.55884-1-mlombard@redhat.com


Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>