regulator: tps6287x: Constify struct regulator_desc

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 <christophe.jaillet@wanadoo.fr>
Link: https://patch.msgid.link/7727e493490d37775a653905dfe0cc1d8478f8e0.1725908163.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Mark Brown <broonie@kernel.org>