Input: mma8450 - add device tree probe support

It adds device tree probe support for mma8450 driver.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Eric Miao <eric.miao@linaro.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>