iscsi-target: Avoid unnecessary t_state_lock during unsolicited data-out check

In modern iscsi-target code, the setup and I/O submission is done within a
single process context, so there is no need to acquire se_cmd->t_state_lock while
checking SCF_SUPPORTED_SAM_OPCODE for determining when unsolicited data-out
should be dumped.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Roland Dreier <roland@kernel.org>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Moussa Ba <moussaba@micron.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>