MAINTAINERS: of: Add Saravana Kannan

Adding myself as a second maintainer for Open Firmware and Device Tree
to help Rob out with reviews and other maintainer work.

Cc: devicetree@vger.kernel.org
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20240210231513.111117-1-saravanak@google.comSigned-off-by: Rob Herring <robh@kernel.org>

MAINTAINERS

@@ -16359,6 +16359,7 @@ F:	drivers/infiniband/ulp/opa_vnic
 
 OPEN FIRMWARE AND FLATTENED DEVICE TREE
 M:	Rob Herring <robh@kernel.org>
+M:	Saravana Kannan <saravanak@google.com>
 L:	devicetree@vger.kernel.org
 S:	Maintained
 W:	http://www.devicetree.org/