gralloc: fix warnings

Fix LP64 pointer casting warnings, unused parameters, and
turn off missing initializer warnings.

Change-Id: Idb70f4534282fed64ae81cb1e154d3f5b93091b0
diff --git a/modules/gralloc/gralloc_priv.h b/modules/gralloc/gralloc_priv.h
index 86a5d52..9f32d58 100644
--- a/modules/gralloc/gralloc_priv.h
+++ b/modules/gralloc/gralloc_priv.h
@@ -75,7 +75,7 @@
     int     offset;
 
     // FIXME: the attributes below should be out-of-line
-    int     base;
+    uintptr_t base;
     int     pid;
 
 #ifdef __cplusplus