MAINTAINERS: Renesas Pin Controllers are supported

Change "PIN CONTROLLER - RENESAS" section from Maintained to Supported.
This brings it in line with my other "+renesas" entries.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200518081836.23890-1-geert+renesas@glider.be