HID: wacom: add USB_HID dependency

The driver has gained a compile-time dependency that we should
express in Kconfig to avoid this link error:

drivers/hid/wacom_sys.o: In function `wacom_parse_and_register':
wacom_sys.c:(.text+0x2eec): undefined reference to `usb_hid_driver'

Fixes: 09dc28ac

 ("HID: wacom: Improve generic name generation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>