pinctrl: sh-pfc: Use u32 to store register data

As PFC registers are either 8, 16, or 32 bits wide, use u32 (mostly
replacing unsigned long) to store (parts of) register values and masks.

Switch the shadow register operations from {set,clear}_bit() to plain C
bit operations, as the former can operate on long data only.

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