The structure iscsi_cmd naming is used by the iSCSI initiator driver.
Rename the target cmd to iscsit_cmd to have more readable code.

Link: https://lore.kernel.org/r/20220428092939.36768-1-mgurtovoy@nvidia.comReviewed-by: NMike Christie <michael.christie@oracle.com>
Signed-off-by: NMax Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>