- Stopping and releasing the device causes the ADF to purge any remaining pages,
thus only the first page gets properly scanned (observed with Samsung
SCX-4729FW).
- Instead, when sourcing from the ADF, at each page's completion it should
continue and issue "OBJECT POSITION" command to proceed to the next page.
- Once all pages have been processed, the subsequent "OBJECT POSITION" command
returns the proper "CHECK CONDITION" status  (ADF is empty) and triggers the
device stop and release.
- Additionally, the status of the ADF (loaded/empty) needs to be requeried
at the `sane_start()` for proper handling of the "Auto" mode. Otherwise,
the scanning session retains the ADF state from the start of the session,
even though ADF will become empty. Thus the "Auto" mode will not properly
switch to Flatbed as intended in the client application (observed in
Simple-Scan).

> NOTE: the initial "READ" command in `sane_start()` is extraneous an...