MAINTAINERS: add dts/vendor/arduino/ to Arduino Platforms section

Files in that directory relate to Arduino hardware products, so it makes
sense to include them in the Arduino Platforms section.

Signed-off-by: Luca Burelli <[email protected]>

Author: pillo79

MAINTAINERS.yml

@@ -337,6 +337,7 @@ Arduino Platforms:
     - boards/arduino/
     - boards/shields/arduino_*/
     - drivers/*/*modulino*
+    - dts/vendor/arduino/
 
 Base OS:
   status: maintained