Visible only if COMPILE_TEST is enabled, this allows to include the
driver in build tests.
Acked-by: NNeil Armstrong <narmstrong@baylibre.com>
Reviewed-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: NPhilipp Zabel <p.zabel@pengutronix.de>