scsi: iscsi: Allow iscsi_if_stop_conn() to be called from kernel

scsi: iscsi: Allow iscsi_if_stop_conn() to be called from kernel

iscsi_if_stop_conn() is only called from the userspace interface but in a
subsequent commit we will want to call it from the kernel interface to
allow drivers like qedi to remove sessions from inside the kernel during
shutdown. This removes the iscsi_uevent code from iscsi_if_stop_conn() so we
can call it in a new helper.

Link: https://lore.kernel.org/r/20220616222738.5722-3-michael.christie@oracle.com
Tested-by: Nilesh Javali <njavali@marvell.com>
Reviewed-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>