sh-pfc: r8a73a4: Add bias (pull-up/down) pinconf support

Implement pull-up/down support for r8a73a4 similar to the implementation
for sh73a0.

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