USB HID: don't warn on idVendor == 0

It turns out that there are broken devices out there that incorrectly
report VID/PID as 0x000, see http://lkml.org/lkml/2007/4/27/496

Therefore we should not confuse users by dumping warnings and stacktraces
in such situation. It is not possible to add quirks for such horribly
broken devices, but currently that's not needed.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>