ARM: dts: N9/N950: Add support for accelerometer

Signed-off-by: Filip Matijević <filip.matijevic.pz@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Tony Lindgren <tony@atomide.com>