Rover: default magnetometer to enabled

will be disabled by auto-detect code if not attached

APMrover2/config.h

@@ -82,7 +82,6 @@
 # define CONFIG_RELAY      DISABLED
 # define MAG_ORIENTATION   AP_COMPASS_APM2_SHIELD
 # define CONFIG_SONAR_SOURCE SONAR_SOURCE_ANALOG_PIN
-# define MAGNETOMETER ENABLED
 # define A_LED_PIN        27
 # define B_LED_PIN        26
 # define C_LED_PIN        25
@@ -266,7 +265,7 @@
 //////////////////////////////////////////////////////////////////////////////
 //  MAGNETOMETER
 #ifndef MAGNETOMETER
-# define MAGNETOMETER			DISABLED
+# define MAGNETOMETER			ENABLED
 #endif
 #ifndef MAG_ORIENTATION
 # define MAG_ORIENTATION		AP_COMPASS_COMPONENTS_DOWN_PINS_FORWARD