regulator: tps6594-regulator: Constify struct tps6594_regulator_irq_type

regulator: tps6594-regulator: Constify struct tps6594_regulator_irq_type

'struct tps6594_regulator_irq_type' are not modified in this driver.

Constifying this structure moves some data to a read-only section, so
increases overall security.

On a x86_64, with allmodconfig, as an example:
Before:
======
   text	   data	    bss	    dec	    hex	filename
  25645	  14480	     64	  40189	   9cfd	drivers/regulator/tps6594-regulator.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
  27949	  12176	     64	  40189	   9cfd	drivers/regulator/tps6594-regulator.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://patch.msgid.link/1446fb1938f3f38115be3e53f5dda3c8bb0ba5a1.1748103005.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Mark Brown <broonie@kernel.org>