gralloc: Allow system heap to be uncached.

Remove an old check that prevented this from happening.

Change-Id: I938b11b27e58fc38a679dc55e31e7b51eb86bd3a
diff --git a/libgralloc/alloc_controller.cpp b/libgralloc/alloc_controller.cpp
index 46acd56..79b453d 100644
--- a/libgralloc/alloc_controller.cpp
+++ b/libgralloc/alloc_controller.cpp
@@ -75,9 +75,6 @@
 
 static bool useUncached(int usage)
 {
-    // System heaps cannot be uncached
-    if(usage & GRALLOC_USAGE_PRIVATE_SYSTEM_HEAP)
-        return false;
     if (usage & GRALLOC_USAGE_PRIVATE_UNCACHED)
         return true;
     return false;