of: Provide dummy of_device_compatible_match() for compile-testing

Most of_device_*() functions have dummy versions for CONFIG_OF=n,
but of_device_compatible_match() hasn't.  Fix that to improve the
ability to do compile-testing.

Fixes: b9c13fe3 ("dt: Add of_device_compatible_match()")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>