Bugfix: corrects orientation of magnetometer raw values

The magnetomer raw values were not being rotated in the same direction as
the scaled values. This meant that if the rotation was set to ROTATION_NONE,
the raw values and scaled values were off by 180 degrees.

src/drivers/hmc5883/hmc5883.cpp

@@ -987,8 +987,8 @@ HMC5883::collect()
 	 * to align the sensor axes with the board, x and y need to be flipped
 	 * and y needs to be negated
 	 */
-	new_report.x_raw = report.y;
-	new_report.y_raw = -report.x;
+	new_report.x_raw = -report.y;
+	new_report.y_raw = report.x;
 	/* z remains z */
 	new_report.z_raw = report.z;