as a module

Without a GPL-compatible license this driver cannot be built as a module,
because the platform_driver_* API is only exported to GPL modules.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@pengutronix.de>
Acked-by: NEric Miao <eric.miao@marvell.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>