pinctrl: rza1: constify pinconf_ops, pinctrl_ops, and pinmux_ops structures

This pinmux_ops structure is only stored in the const pmxops field
of a pinctrl_desc structure. Make the pinmux_ops structure const as
well.

Done with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>