HID: fix error message in hid_open_report()

On HID report descriptor parsing error the code displays bogus
pointer instead of error offset (subtracts start=NULL from end).
Make the message more useful by displaying correct error offset
and include total buffer size for reference.

This was carried over from ancient times - "Fixed" commit just
promoted the message from DEBUG to ERROR.

Cc: stable@vger.kernel.org
Fixes: 8c3d52fc

 ("HID: make parser more verbose about parsing errors by default")
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>