identity: Use "credstore" for LOG_TAG everywhere.

Currently we're using file-specific tags which makes it hard for
people looking at logcat to infer it's actually from credstore and it
also complicates filtering. Just use "credstore" everywhere.

Also change logging level from ERROR to INFO in the message
"Registered binder service" which is logged on startup.

Bug: None
Test: Compiles + manual inspection via logcat
Test: atest android.security.identity.cts (on goldfish)
Change-Id: I336d1a4e4e10b87fd3f08a5046cf5e13f09c9cb6
diff --git a/identity/Util.cpp b/identity/Util.cpp
index cd29017..3a46bca 100644
--- a/identity/Util.cpp
+++ b/identity/Util.cpp
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#define LOG_TAG "Util"
+#define LOG_TAG "credstore"
 
 #include <fcntl.h>
 #include <stdlib.h>