EV_yaw: reset ev_to_ekf to identity when yaw is reset to EV

Otherwise, the old rotation matrix is used and not updated anymore
because the EKF is fusing EV yaw data.

EKF/ekf_helper.cpp

@@ -532,6 +532,7 @@ bool Ekf::resetYawToEv()
 	const float yaw_new_variance = fmaxf(_ev_sample_delayed.angVar, sq(1.0e-2f));
 
 	resetQuatStateYaw(yaw_new, yaw_new_variance, true);
+	_R_ev_to_ekf.setIdentity();
 
 	return true;
 }