refactor hmc5883: use driver base class

Removes the calibration on startup, as these values were overwritten by
the system calibration values anyway.
So the only difference is that if all calibration scales were equal to 1,
the driver startup would have failed.

boards/px4/fmu-v4/init/rc.board_sensors

@@ -15,7 +15,7 @@ fmu sensor_reset 50
 
 
 # External I2C bus
-hmc5883 -C -T -X start
+hmc5883 -T -X start
 lis3mdl -X start
 ist8310 -X start
 qmc5883 -X start
@@ -32,7 +32,7 @@ then
 fi
 
 # hmc5883 internal SPI bus is rotated 90 deg yaw
-if ! hmc5883 -C -T -S -R 2 start
+if ! hmc5883 -T -S -R 2 start
 then
 	# lis3mdl internal SPI bus is rotated 90 deg yaw
 	lis3mdl start