pw_kvs: Use PW_LOG_MODULE_NAME

Sets PW_LOG_MODULE_NAME in KVS source files that use logging to ensure
logs messages are attributed to this module.

Change-Id: Ia8386b26a8a1c775090a7831532c72e8ee9f313c
diff --git a/pw_kvs/entry_cache.cc b/pw_kvs/entry_cache.cc
index 4528ab2..599ae80 100644
--- a/pw_kvs/entry_cache.cc
+++ b/pw_kvs/entry_cache.cc
@@ -12,6 +12,8 @@
 // License for the specific language governing permissions and limitations under
 // the License.
 
+#define PW_LOG_MODULE_NAME "KVS"
+
 #include "pw_kvs/internal/entry_cache.h"
 
 #include <cinttypes>