leds: is31fl319x: Constify struct regmap_config

'is31fl3190_regmap_config' and 'is31fl3196_regmap_config' are not modified
in this diver and are only used as a const struct regmap_config.

Constifying these structures moves some data to a read-only section, so
increase overall security.

On a x86_64, with allmodconfig:
Before:
   text	   data	    bss	    dec	    hex	filename
  13827	   2002	     32	  15861	   3df5	drivers/leds/leds-is31fl319x.o

After:
   text	   data	    bss	    dec	    hex	filename
  14467	   1370	     32	  15869	   3dfd	drivers/leds/leds-is31fl319x.o
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/82a5cb26ff8af1865a790286bdbc3c4a2bd149f1.1714892598.git.christophe.jaillet@wanadoo.frSigned-off-by: Lee Jones <lee@kernel.org>

drivers/leds/leds-is31fl319x.c

@@ -140,7 +140,7 @@ static const struct reg_default is31fl3190_reg_defaults[] = {
 	{ IS31FL3190_PWM(2), 0x00 },
 };
 
-static struct regmap_config is31fl3190_regmap_config = {
+static const struct regmap_config is31fl3190_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.max_register = IS31FL3190_RESET,
@@ -178,7 +178,7 @@ static const struct reg_default is31fl3196_reg_defaults[] = {
 	{ IS31FL3196_PWM(8), 0x00 },
 };
 
-static struct regmap_config is31fl3196_regmap_config = {
+static const struct regmap_config is31fl3196_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.max_register = IS31FL3196_REG_CNT,