ALSA: rawmidi: More constification

Apply const prefix to the static flag info table.

Just for minor optimization and no functional changes.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Takashi Iwai <[e-mail]>

sound/core/rawmidi.c

···
 {
 	struct snd_rawmidi_substream *substream;
 	struct snd_rawmidi_str *s = &rmidi->streams[stream];
-	static unsigned int info_flags[2] = {
+	static const unsigned int info_flags[2] = {
 		[SNDRV_RAWMIDI_STREAM_OUTPUT] = SNDRV_RAWMIDI_INFO_OUTPUT,
 		[SNDRV_RAWMIDI_STREAM_INPUT] = SNDRV_RAWMIDI_INFO_INPUT,
 	};