HID: input: Map unknown consumer page codes to KEY_UNKNOWN

Currently unknown consumer page codes are ignored, which means that they cannot
later be mapped from userspace using udev / hwdb. Map them to KEY_UNKNOWN, so
that userspace can remap them for keyboards which make up their own consumer
page codes.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>