regulator: max77857: Constify struct regmap_config

`max77857_remgap_config` is not modified and can be declared as const to
move its data to a read-only section.

Signed-off-by: Javier Carrasco <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/max77857-regulator.c

···
 	}
 }
 
-static struct regmap_config max77857_regmap_config = {
+static const struct regmap_config max77857_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.cache_type = REGCACHE_MAPLE,