x11-toolkits/wlroots: limit hwdata dependency to DRM as build only

pnp.ids is converted to pnpids.c, so won't pick up changes without rebuild.
pnp.ids is also unused when nesting on X11 or Wayland (WLR_BACKENDS != drm).
https://gitlab.freedesktop.org/wlroots/wlroots/-/commit/eec95e3d5e1a