regulator: tps6287x: Constify struct regulator_desc

'struct regulator_desc' is not modified in this driver.

Constifying this structure moves some data to a read-only section, so
increases overall security, especially when the structure holds some
function pointers.

On a x86_64, with allmodconfig:
Before:
======
text data bss dec hex filename
4974 736 16 5726 165e drivers/regulator/tps6287x-regulator.o

After:
=====
text data bss dec hex filename
5294 416 16 5726 165e drivers/regulator/tps6287x-regulator.o

--
Compile tested only

Signed-off-by: Christophe JAILLET <[e-mail]>
Link: https://patch.msgid.link/7727e49349[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/tps6287x-regulator.c

···
 	.set_ramp_delay = regulator_set_ramp_delay_regmap,
 };
 
-static struct regulator_desc tps6287x_reg = {
+static const struct regulator_desc tps6287x_reg = {
 	.name = "tps6287x",
 	.owner = THIS_MODULE,
 	.ops = &tps6287x_regulator_ops,