meson: move wayland_drm_protocol generation to wayland-drm

meson: move wayland_drm_protocol generation to wayland-drm

These files are needed by both vulkan wayland-wsi and by egl
wayland-wsi, since the XML file is in src/egl/wayland/wayland-drm and we
can include this directory in such a way that it will be loaded before
egl and vulkan this allows us to avoid multiple calls to the same
generator.

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-and-Tested-by: Eric Engestrom <eric@engestrom.ch>