ekf2: new kconfig to enable/disable GNSS (enabled by default)

src/modules/ekf2/EKF/CMakeLists.txt

@@ -42,9 +42,6 @@ list(APPEND EKF_SRCS
 	estimator_interface.cpp
 	fake_height_control.cpp
 	fake_pos_control.cpp
-	gnss_height_control.cpp
-	gps_checks.cpp
-	gps_control.cpp
 	gravity_fusion.cpp
 	height_control.cpp
 	imu_down_sampler.cpp
@@ -84,6 +81,14 @@ if(CONFIG_EKF2_EXTERNAL_VISION)
 	)
 endif()
 
+if(CONFIG_EKF2_GNSS)
+	list(APPEND EKF_SRCS
+		gnss_height_control.cpp
+		gps_checks.cpp
+		gps_control.cpp
+	)
+endif()
+
 if(CONFIG_EKF2_GNSS_YAW)
 	list(APPEND EKF_SRCS gps_yaw_fusion.cpp)
 endif()