Switch to using keymaster_defs.h from libhardware.

In the past it was convenient to have a local copy of this file
(for reasons which no longer apply).

Change-Id: Ie4a6f80abd16c77c0252f64ec65f2beeeef9a7a3
diff --git a/key.h b/key.h
index 982367f..fab7816 100644
--- a/key.h
+++ b/key.h
@@ -17,8 +17,8 @@
 #ifndef SYSTEM_KEYMASTER_KEY_H_
 #define SYSTEM_KEYMASTER_KEY_H_
 
+#include <hardware/keymaster_defs.h>
 #include <keymaster/authorization_set.h>
-#include <keymaster/keymaster_defs.h>
 #include <keymaster/logger.h>
 
 namespace keymaster {