examples: use new component registration api

* Original commit: espressif/esp-idf@6771eead80

examples/common_components/protocol_examples_common/CMakeLists.txt

@@ -1,5 +1,2 @@
-set(COMPONENT_SRCS "connect.c"
-                   "stdin_out.c")
-set(COMPONENT_ADD_INCLUDEDIRS "include")
-
-register_component()
+idf_component_register(SRCS "connect.c" "stdin_out.c"
+                    INCLUDE_DIRS "include")

examples/protocols/mdns/main/CMakeLists.txt

@@ -1,4 +1,2 @@
-set(COMPONENT_SRCS "mdns_example_main.c")
-set(COMPONENT_ADD_INCLUDEDIRS ".")
-
-register_component()
+idf_component_register(SRCS "mdns_example_main.c"
+                    INCLUDE_DIRS ".")