Since the removal of the legacy block layer there is only one completion
function left in the SCSI core, namely scsi_mq_done(). Rename it into
scsi_done(). Export that function to allow SCSI LLDs to call it directly.

Link: https://lore.kernel.org/r/20211007202923.2174984-3-bvanassche@acm.orgReviewed-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>