gralloc: Do not initialize reserved field

The gralloc header was updated with a new extension for locking
ycbcr - initializing the reserved field breaks the build.

Change-Id: I88d26bbd2005041e9396c8f5a0d2fe18f9c4055e
diff --git a/libgralloc/gralloc.cpp b/libgralloc/gralloc.cpp
index 3bb5533..2567300 100644
--- a/libgralloc/gralloc.cpp
+++ b/libgralloc/gralloc.cpp
@@ -80,7 +80,6 @@
     lock: gralloc_lock,
     unlock: gralloc_unlock,
     perform: gralloc_perform,
-    reserved_proc: {0},
       },
 framebuffer: 0,
 fbFormat: 0,