Fix extern "C" guards.

Change-Id: Ibc8e023e3712903dbcbfac5fc64223e32775fe40
diff --git a/include/hardware/keymaster_defs.h b/include/hardware/keymaster_defs.h
index 9eb0c0f..77067d5 100644
--- a/include/hardware/keymaster_defs.h
+++ b/include/hardware/keymaster_defs.h
@@ -21,7 +21,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#ifndef __cplusplus
+#ifdef __cplusplus
 extern "C" {
 #endif  // __cplusplus
 
@@ -510,7 +510,7 @@
     }
 }
 
-#ifndef __cplusplus
+#ifdef __cplusplus
 }  // extern "C"
 #endif  // __cplusplus