kbuild: disable new dtc graph and unit-address warnings

dtc gained some new warnings for OF graphs and unique unit addresses,
but they are currently much too noisy. So turn off
'graph_child_address', 'graph_port', and 'unique_unit_address' warnings
by default. They can be enabled by building dtbs with W=1.
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: linux-kbuild@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

scripts/Makefile.lib

@@ -251,6 +251,9 @@ DTC_FLAGS += -Wno-unit_address_vs_reg \
 	-Wno-unit_address_format \
 	-Wno-avoid_unnecessary_addr_size \
 	-Wno-alias_paths \
+	-Wno-graph_child_address \
+	-Wno-graph_port \
+	-Wno-unique_unit_address \
 	-Wno-pci_device_reg
 endif