regulator: max77620-regulator: constify regulator_ops structure

Declare regulator_ops structure as const as it is only stored in the ops
field of a regulator_desc structure. This field is of type const, so
regulator_ops structures having this property can be made const too.

File size before: drivers/regulator/max77620-regulator.o
   text	   data	    bss	    dec	    hex	filename
   4811	   6992	      0	  11803	   2e1b regulator/max77620-regulator.o

File size after: drivers/regulator/max77620-regulator.o
   text	   data	    bss	    dec	    hex	filename
   5075	   6720	      0	  11795	   2e13 regulator/max77620-regulator.o

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/max77620-regulator.c

@@ -644,7 +644,7 @@ static int max77620_of_parse_cb(struct device_node *np,
 	return max77620_init_pmic(pmic, desc->id);
 }
 
-static struct regulator_ops max77620_regulator_ops = {
+static const struct regulator_ops max77620_regulator_ops = {
 	.is_enabled = max77620_regulator_is_enabled,
 	.enable = max77620_regulator_enable,
 	.disable = max77620_regulator_disable,