Fix misc-macro-parentheses warnings.

Bug: 28705665
Change-Id: I1ad468741c6f117817099d2ba87374dce2b776a9
diff --git a/drm/drmserver/DrmManager.cpp b/drm/drmserver/DrmManager.cpp
index 7c53fea..18b9a3b 100644
--- a/drm/drmserver/DrmManager.cpp
+++ b/drm/drmserver/DrmManager.cpp
@@ -33,7 +33,7 @@
 #include "DrmManager.h"
 #include "ReadWriteUtils.h"
 
-#define DECRYPT_FILE_ERROR -1
+#define DECRYPT_FILE_ERROR (-1)
 
 using namespace android;