tune_control: update comment

msg/tune_control.msg

 # This message is used to control the tunes, when the tune_id is set to CUSTOM
 # then the frequency, duration are used otherwise those values are ignored.
 
-uint8 tune_id
+uint8 tune_id        # tune_id corresponding to TuneID::* from the tune_defaults.h in the tunes library
 uint8 tune_override  # if set to 1 the tune which is playing will be stopped and the new started
 uint16 frequency     # in Hz
 uint32 duration      # in us
-uint32 silence 		 # in us
+uint32 silence	     # in us
 uint8 strength       # value between 0-100 if supported by backend
 
 uint8 STRENGTH_NORMAL = 40