ASoc: rt5631: Constify static struct coeff_clk_div

coeff_div is only read from, so make it const to show the intent.
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20210224211918.39109-5-rikard.falkeborn@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt5631.c

@@ -1283,7 +1283,7 @@ static const struct pll_div codec_slave_pll_div[] = {
 	{3072000,  12288000,  0x0a90},
 };
 
-static struct coeff_clk_div coeff_div[] = {
+static const struct coeff_clk_div coeff_div[] = {
 	/* sysclk is 256fs */
 	{2048000,  8000 * 32,  8000, 0x1000},
 	{2048000,  8000 * 64,  8000, 0x0000},