pinctrl: sh-pfc: Use unsigned int for register/field widths and offsets

As register and field widths and offsets are in the range 1..32, use
unsigned int (mostly replacing unsigned long) to store them in local
variables and for passing them around.

Move to one variable per line, move variables to the beginning of the
block where they are used, and drop superfluous initializations while we
are at it.

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>