pinctrl: sh-pfc: sh73a0: Remove unnecessary SoC data allocation

The SoC data structure allocated at init time only holds a regulator
pointer that is only used in the init function. Replace it with a local
variable and get rid of the SoC data structure allocation altogether.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>