MAINTAINERS: add i2c to the excludes for Documentation

I'll handle these myself but thanks for providing the fallback!
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

MAINTAINERS

@@ -4487,6 +4487,7 @@ F:	scripts/kernel-doc
 X:	Documentation/ABI/
 X:	Documentation/acpi/
 X:	Documentation/devicetree/
+X:	Documentation/i2c/
 X:	Documentation/media/
 X:	Documentation/power/
 X:	Documentation/spi/