EKF: Reset yaw gyro bias learning when resuming use of magnetometer
EKF: Reset yaw gyro bias learning when resuming use of magnetometer

The previous lack of yaw drift constraint will also mean that the yaw gyro bias estimate is likely to be incorrect and needs to be re-learned.

PX4/ecl,PX4/ecl,PX4/ecl,PX4/ecl,PX4/ecl