scsi: target: Export fabric driver direct submit settings

scsi: target: Export fabric driver direct submit settings

This exports the fabric driver's direct submit settings, so users know what
the driver supports. It will be helpful when they are exporting a device
through different targets and one doesn't support direct submission.

The new files allow the fabric to report what submission types they default
to and if they support direct submission:

default_submit_type:

 1 - TARGET_DIRECT_SUBMIT - If the user has not requested a specific value
     then the fabric requests direct submission.

 2 - TARGET_QUEUE_SUBMIT - If the user has not requested a specific value
     then the fabric requests queued submission.

Note that these fabric values are based on what the fabric driver currently
defaults to for compat with exiting setups.

direct_submit_supported:

 0 - The fabric does not support direct submission.

 1 - The fabric supports direct submission.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230928020907.5730-8-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>