MAINTAINERS: Add Realtek arm DT files

Add a file pattern for 32-bit arm DT files being added.
Signed-off-by: Andreas Färber <afaerber@suse.de>

MAINTAINERS

@@ -2270,6 +2270,7 @@ L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 L:	linux-realtek-soc@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
 F:	Documentation/devicetree/bindings/arm/realtek.yaml
+F:	arch/arm/boot/dts/rtd*
 F:	arch/arm/mach-realtek/
 F:	arch/arm64/boot/dts/realtek/