scsi: core: Extend struct scsi_exec_args

Allow SCSI LLDs to specify SCMD_* flags.

Link: https://lore.kernel.org/r/20230210193258.4004923-2-bvanassche@acm.org


Cc: Mike Christie <michael.christie@oracle.com>
Cc: John Garry <john.g.garry@oracle.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>