ASoC: rcar: mark device data as constant

A driver's device data should and can be const. This is a follow-up on
commit 33187fb4 (ASoC: rsnd: constify of_device_id array) which
marked the of_device_id as const.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sh/rcar/core.c

@@ -99,11 +99,11 @@
 #define RSND_RATES SNDRV_PCM_RATE_8000_96000
 #define RSND_FMTS (SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S16_LE)
 
-static struct rsnd_of_data rsnd_of_data_gen1 = {
+static const struct rsnd_of_data rsnd_of_data_gen1 = {
 	.flags = RSND_GEN1,
 };
 
-static struct rsnd_of_data rsnd_of_data_gen2 = {
+static const struct rsnd_of_data rsnd_of_data_gen2 = {
 	.flags = RSND_GEN2,
 };