scsi: iscsi: Fix incorrect error path labels for flashnode operations

scsi: iscsi: Fix incorrect error path labels for flashnode operations

Correct the error handling goto labels used when host lookup fails in
various flashnode-related event handlers:

 - iscsi_new_flashnode()
 - iscsi_del_flashnode()
 - iscsi_login_flashnode()
 - iscsi_logout_flashnode()
 - iscsi_logout_flashnode_sid()

scsi_host_put() is not required when shost is NULL, so jumping to the
correct label avoids unnecessary operations. These functions previously
jumped to the wrong goto label (put_host), which did not match the
intended cleanup logic.

Use the correct exit labels (exit_new_fnode, exit_del_fnode, etc.) to
ensure proper error handling.  Also remove the unused put_host label
under iscsi_new_flashnode() as it is no longer needed.

No functional changes beyond accurate error path correction.

Fixes: c6a4bb2ef596 ("[SCSI] scsi_transport_iscsi: Add flash node mgmt support")
Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Link: https://lore.kernel.org/r/20250530193012.3312911-1-alok.a.tiwari@oracle.com
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>