pinctrl: sh-pfc: r8a7791: Add VIN pins

This adds VIN[0-2] pinmux support to r8a7791 SoC.
VIN1 B mirror is also added along with the primary
configuration since it's the only one that provides
access to all 24 data bits on VIN1.

Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>