MAINTAINERS: Add Renesas SoC DT bindings to Renesas Architecture sections

While Renesas SoC DT bindings documents started to appear under
Documentation/devicetree/bindings/soc/renesas, these are not yet covered
by the file and directory patterns in the Renesas ARM/ARM64 Architecture
sections.

Add the missing patterns.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/f99c03a95a103517418f0b23d3da45e0dd0ffb3b.1655456310.git.geert+renesas@glider.be