mfd: davinci_voicecodec: Constify struct regmap_config

The regmap_config struct may be const because it is not modified by the
driver and regmap_init() accepts pointer to const.
Signed-off-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/davinci_voicecodec.c

@@ -33,7 +33,7 @@
 
 #include <linux/mfd/davinci_voicecodec.h>
 
-static struct regmap_config davinci_vc_regmap = {
+static const struct regmap_config davinci_vc_regmap = {
 	.reg_bits = 32,
 	.val_bits = 32,
 };