STE Multimedia Fix [2/4]
sensorservice: Add legacy sensors fusion.

This change allows devices with accelerometer & magnetometer but
without gyroscope to still get virtual sensors such as Gravity,
Linear Acceleration, Orientation & Rotation Vector.

Can be disabled with BOARD_USE_LEGACY_SENSORS_FUSION := false

Change-Id: Ibb90b70845c766ab52c843557446e34649a7d6d9