of/unittest: Fix I2C bus unit-address error

dtc has new checks for I2C buses. Fix the warnings in unit-addresses in the unittests.

drivers/of/unittest-data/testcases.dtb: Warning (i2c_bus_reg): /testcase-data/overlay-node/test-bus/i2c-test-bus/test-unittest14/i2c@0/test-mux-dev: I2C bus unit address format error, expected "20" drivers/of/unittest-data/overlay_15.dtb: Warning (i2c_bus_reg): /fragment@0/__overlay__/test-unittest15/i2c@0/test-mux-dev: I2C bus unit address format error, expected "20"

---
 drivers/of/unittest-data/overlay_15.dts     | 4 ++--
 drivers/of/unittest-data/tests-overlay.dtsi | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

index b98f2514df4b..5728490474f6 100644
@@ -20,8 +20,8 @@
 			#size-cells = <0>;
 			reg = <0>;
 
-			test-mux-dev {
-				reg = <32>;
+			test-mux-dev@20 {
+				reg = <0x20>;
 				compatible = "unittest-i2c-dev";
 				status = "okay";
 			};

index 25cf397b8f6b..4ea024d908ee 100644
@@ -103,8 +103,8 @@
 							#size-cells = <0>;
 							reg = <0>;
 
-							test-mux-dev {
-								reg = <32>;
+							test-mux-dev@20 {
+								reg = <0x20>;
 								compatible = "unittest-i2c-dev";
 								status = "okay";
 							};

2.17.1