scsi: core: Merge scsi_internal_device_block() and device_block()

scsi_internal_device_block() is only called from device_block().  Merge the
two functions, and call the result scsi_device_block(), as the name
device_block() is confusingly generic.

Signed-off-by: Martin Wilck <mwilck@suse.com>
Link: https://lore.kernel.org/r/20230614103616.31857-4-mwilck@suse.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>