ALSA: seq: Constify snd_rawmidi_ops

Now snd_rawmidi_ops is maintained as a const pointer in snd_rawmidi,
we can constify the definitions.
Reviewed-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/core/seq/seq_virmidi.c

@@ -349,13 +349,13 @@ static int snd_virmidi_unuse(void *private_data,
  *  Register functions
  */
 
-static struct snd_rawmidi_ops snd_virmidi_input_ops = {
+static const struct snd_rawmidi_ops snd_virmidi_input_ops = {
 	.open = snd_virmidi_input_open,
 	.close = snd_virmidi_input_close,
 	.trigger = snd_virmidi_input_trigger,
 };
 
-static struct snd_rawmidi_ops snd_virmidi_output_ops = {
+static const struct snd_rawmidi_ops snd_virmidi_output_ops = {
 	.open = snd_virmidi_output_open,
 	.close = snd_virmidi_output_close,
 	.trigger = snd_virmidi_output_trigger,