HID: input: fix a4tech horizontal wheel custom usage

Some a4tech mice use the 'GenericDesktop.00b8' usage to inform whether
the previous wheel report was horizontal or vertical. Before
c01908a1 ("HID: input: add mapping for "Toggle Display" key") this
usage was being mapped to 'Relative.Misc'. After the patch it's simply
ignored (usage->type == 0 & usage->code == 0). Which ultimately makes
hid-a4tech ignore the WHEEL/HWHEEL selection event, as it has no
usage->type.

We shouldn't rely on a mapping for that usage as it's nonstandard and
doesn't really map to an input event. So we bypass the mapping and make
sure the custom event handling properly handles both reports.

Fixes: c01908a1

 ("HID: input: add mapping for "Toggle Display" key")
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>