ALSA: ak4531: More constification

Apply const prefix to the initial register map.

Just for minor optimization and no functional changes.

Link: https://lore.kernel.org/r/20200105144823.29547-60-tiwai@suse.deSigned-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/ak4531_codec.c

@@ -335,7 +335,7 @@ static int snd_ak4531_dev_free(struct snd_device *device)
 	return snd_ak4531_free(ak4531);
 }
 
-static u8 snd_ak4531_initial_map[0x19 + 1] = {
+static const u8 snd_ak4531_initial_map[0x19 + 1] = {
 	0x9f,		/* 00: Master Volume Lch */
 	0x9f,		/* 01: Master Volume Rch */
 	0x9f,		/* 02: Voice Volume Lch */