hwmon: (pmbus/mpq7932) 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
increase overall security, especially when the structure holds some
function pointers.

This also makes mpq7932_regulators_desc consistent with
mpq7932_regulators_desc_one which is already a "static const struct
regulator_desc".

On a x86_64, with allmodconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
   3516	   2264	      0	   5780	   1694	drivers/hwmon/pmbus/mpq7932.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
   5396	    384	      0	   5780	   1694	drivers/hwmon/pmbus/mpq7932.o
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Message-ID: <c0585a07547ec58d99a5bff5e02b398114bbe312.1725784343.git.christophe.jaillet@wanadoo.fr>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/mpq7932.c

@@ -35,7 +35,7 @@ struct mpq7932_data {
 };
 
 #if IS_ENABLED(CONFIG_SENSORS_MPQ7932_REGULATOR)
-static struct regulator_desc mpq7932_regulators_desc[] = {
+static const struct regulator_desc mpq7932_regulators_desc[] = {
 	PMBUS_REGULATOR_STEP("buck", 0, MPQ7932_N_VOLTAGES,
 			     MPQ7932_UV_STEP, MPQ7932_BUCK_UV_MIN),
 	PMBUS_REGULATOR_STEP("buck", 1, MPQ7932_N_VOLTAGES,