libgui: Fix buffer age on 64-bit targets

Changes a %llu to a PRIu64 to fix compilation on 64-bit targets.

Change-Id: I8ba982662dbe8ee2e1e47c4f6ce4bbdbe2020960
diff --git a/libs/gui/BufferQueueProducer.cpp b/libs/gui/BufferQueueProducer.cpp
index b8df436..7251d36 100644
--- a/libs/gui/BufferQueueProducer.cpp
+++ b/libs/gui/BufferQueueProducer.cpp
@@ -347,7 +347,8 @@
                     mCore->mFrameCounter + 1 - mSlots[found].mFrameNumber;
         }
 
-        BQ_LOGV("dequeueBuffer: setting buffer age to %llu", mCore->mBufferAge);
+        BQ_LOGV("dequeueBuffer: setting buffer age to %" PRIu64,
+                mCore->mBufferAge);
 
         if (CC_UNLIKELY(mSlots[found].mFence == NULL)) {
             BQ_LOGE("dequeueBuffer: about to return a NULL fence - "