soc: mediatek: pwrap: Constify struct pmic_wrapper_type

soc: mediatek: pwrap: Constify struct pmic_wrapper_type

'struct pmic_wrapper_type' is not modified in this driver.

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

On a x86_64, with allmodconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
  45336	   8724	     16	  54076	   d33c	drivers/soc/mediatek/mtk-pmic-wrap.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
  45528	   8532	     16	  54076	   d33c	drivers/soc/mediatek/mtk-pmic-wrap.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/5b4b60c5dfd6d8fe893b05cfc96c0e2d67705463.1720331018.git.christophe.jaillet@wanadoo.fr
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>