usbnet: remove vestiges of debug macros

The driver has long since be converted to dynamic debugging.
The internal compile options for more debugging can simply be
deleted.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20220630110741.21314-1-oneukum@suse.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>