MAINTAINERS: Remove Laurent Pinchart as Renesas pinctrl maintainer

Geert Uytterhoeven has long taken over and I'm not involved anymore with
the Renesas pinctrl driver. Remove myself from the maintainers list.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>