scsi: core: Fix the documentation of the scsi_execute() time parameter

The unit of the scsi_execute() timeout parameter is 1/HZ seconds instead of
one second, just like the timeouts used in the block layer. Fix the
documentation header above the definition of the scsi_execute() macro.

Link: https://lore.kernel.org/r/20210709202638.9480-3-bvanassche@acm.org
Fixes: "[SCSI] use scatter lists for all block pc requests and simplify hw handlers" # v2.6.16.28
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>