scsi: iser: Fix @read_stag kernel-doc warning

scsi: iser: Fix @read_stag kernel-doc warning

Correct kernel-doc comments for struct iser_ctrl to prevent warnings:

iser.h:76: warning: Function parameter or struct member 'read_stag' not described in 'iser_ctrl'
iser.h:76: warning: Excess struct member 'reaf_stag' description in 'iser_ctrl'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20240408025425.18778-5-rdunlap@infradead.org
Acked-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>