logd: syscall optimization

- prset(PR_SET_NAME) call once
- No need to call getuid(), should be AID_LOGD

Change-Id: I4dde0b178bc84e711b355cd7677b0dbf905a0634
diff --git a/logd/LogReader.cpp b/logd/LogReader.cpp
index f7df275..745e847 100644
--- a/logd/LogReader.cpp
+++ b/logd/LogReader.cpp
@@ -37,7 +37,11 @@
 }
 
 bool LogReader::onDataAvailable(SocketClient *cli) {
-    prctl(PR_SET_NAME, "logd.reader");
+    static bool name_set;
+    if (!name_set) {
+        prctl(PR_SET_NAME, "logd.reader");
+        name_set = true;
+    }
 
     char buffer[255];