AP_Baro: save some flash and memory on APM2

we don't need the I2C MS5611 driver

libraries/AP_Baro/AP_Baro_MS5611.cpp

@@ -69,7 +69,9 @@ bool volatile AP_Baro_MS5611::_updated;
 
 AP_Baro_MS5611_Serial* AP_Baro_MS5611::_serial = NULL;
 AP_Baro_MS5611_SPI AP_Baro_MS5611::spi;
+#if MS5611_WITH_I2C
 AP_Baro_MS5611_I2C AP_Baro_MS5611::i2c;
+#endif
 
 // SPI Device //////////////////////////////////////////////////////////////////
 
@@ -154,7 +156,7 @@ void AP_Baro_MS5611_SPI::sem_give()
 }
 
 // I2C Device //////////////////////////////////////////////////////////////////
-
+#if MS5611_WITH_I2C
 /** I2C address of the MS5611 on the PX4 board. */
 #define MS5611_ADDR 0x76
 
@@ -225,6 +227,7 @@ void AP_Baro_MS5611_I2C::sem_give()
 {
     _i2c_sem->give();
 }
+#endif // MS5611_WITH_I2C
 
 // Public Methods //////////////////////////////////////////////////////////////
 

libraries/AP_Baro/AP_Baro_MS5611.h

@@ -6,6 +6,13 @@
 #include <AP_HAL.h>
 #include "AP_Baro.h"
 
+#if CONFIG_HAL_BOARD != HAL_BOARD_APM2
+#define MS5611_WITH_I2C 1
+#else
+#define MS5611_WITH_I2C 0
+#endif
+
+
 /** Abstract serial device driver for MS5611. */
 class AP_Baro_MS5611_Serial
 {
@@ -49,6 +56,7 @@ private:
     AP_HAL::Semaphore *_spi_sem;
 };
 
+#if MS5611_WITH_I2C
 /** I2C serial device. */
 class AP_Baro_MS5611_I2C : public AP_Baro_MS5611_Serial
 {
@@ -64,6 +72,7 @@ public:
 private:
     AP_HAL::Semaphore *_i2c_sem;
 };
+#endif // MS5611_WITH_I2C
 
 class AP_Baro_MS5611 : public AP_Baro
 {
@@ -82,7 +91,9 @@ public:
 
     /* Serial port drivers to pass to "init". */
     static AP_Baro_MS5611_SPI spi;
+#if MS5611_WITH_I2C
     static AP_Baro_MS5611_I2C i2c;
+#endif
 
 private:
     void            _calculate();