liblog: remove log_portability.h

__BEGIN_DECLS and __END_DECLS are all that are left, and I can compile
with using normal <sys/cdefs.h>, so hopefully we can remove this at
last.

Test: build
Change-Id: I6df7ef0da027bb91c98806e0f9661d7416ebaa5d
diff --git a/liblog/logd_reader.h b/liblog/logd_reader.h
index 2d032fa..68eef02 100644
--- a/liblog/logd_reader.h
+++ b/liblog/logd_reader.h
@@ -16,10 +16,10 @@
 
 #pragma once
 
+#include <sys/cdefs.h>
 #include <unistd.h>
 
 #include "log/log_read.h"
-#include "log_portability.h"
 
 __BEGIN_DECLS