ALSA: isa: Constify snd_rawmidi_ops

Now snd_rawmidi_ops is maintained as a const pointer in snd_rawmidi,
we can constify the definitions.

Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/isa/wavefront/wavefront_midi.c

@@ -559,14 +559,14 @@ snd_wavefront_midi_start (snd_wavefront_card_t *card)
 	return 0;
 }
 
-struct snd_rawmidi_ops snd_wavefront_midi_output =
+const struct snd_rawmidi_ops snd_wavefront_midi_output =
 {
 	.open =		snd_wavefront_midi_output_open,
 	.close =	snd_wavefront_midi_output_close,
 	.trigger =	snd_wavefront_midi_output_trigger,
 };
 
-struct snd_rawmidi_ops snd_wavefront_midi_input =
+const struct snd_rawmidi_ops snd_wavefront_midi_input =
 {
 	.open =		snd_wavefront_midi_input_open,
 	.close =	snd_wavefront_midi_input_close,