ARM: mmp: Fix failure to remove sram device

[ Upstream commit 4036b29a ]

Make sure in .probe() to set driver data before the function is left to
make it possible in .remove() to undo the actions done.

This fixes a potential memory leak and stops returning an error code in
.remove() that is ignored by the driver core anyhow.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>