pinctrl: sh-pfc: r8a73a4: Allow Multiplatform Build

Add #ifdefs to allow r8a73a4 Multiplatform build. Needed
to enable r8a73a4 Multiplatform support.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>