MAINTAINERS: Add co-maintainer for Renesas Pin Controllers

Add myself as a co-maintainer for Renesas Pin Controllers.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -8351,6 +8351,7 @@ F:	drivers/pinctrl/intel/
 
 PIN CONTROLLER - RENESAS
 M:	Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+M:	Geert Uytterhoeven <geert+renesas@glider.be>
 L:	linux-sh@vger.kernel.org
 S:	Maintained
 F:	drivers/pinctrl/sh-pfc/