hwc: Set ioprio for vsync thread

This reverts commit e334ed34ddf504921195161d2230a3b4156d9a43.

Change-Id: Iceba230b667c0a4c480301bf5d662a9cf82b6df3

exynos4/hal/libhwc/hwcomposer_vsync.cpp

@@ -17,6 +17,7 @@
 #include "hwcomposer.h"
 #include "hwcomposer_vsync.h"
 
+#include <cutils/iosched_policy.h>
 #include <cutils/threads.h>
 
 #include <utils/threads.h>
@@ -46,6 +47,7 @@ static void *hwc_vsync_thread(void *data)
     char thread_name[64] = HWC_VSYNC_THREAD_NAME;
     prctl(PR_SET_NAME, (unsigned long) &thread_name, 0, 0, 0);
     androidSetThreadPriority(0, HAL_PRIORITY_URGENT_DISPLAY);
+    android_set_ioprio(0, IoSchedClass_RT, 1);
 
     memset(buf, 0, sizeof(buf));