usb/isp1760: Consolidate printouts and remove unused code

Consolidate printouts to use dev_XXX functions instead of an assortment of
printks and driver specific macros. Remove some unused code snippets and struct
members. Remove some unused function parameters and #defines. Change the
"queue_entry" variable name which has different but related meanings in
different places and use "slot" only.

Signed-off-by: Arvid Brodin <arvid.brodin@enea.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>