GBE: Do topological sorting of basicblocks.
GBE: Do topological sorting of basicblocks.

Toplogical sorting have two big advantages:
 1. Sorted basicblocks will reduce unneccesary register pressure.
 2. Sorted basicblocks will make liveness analysis easier.

This patch fix opencv failures:
./opencv_test_video --gtest_filter=OCL_OCL_Video/Mog2_Update.Accuracy/1
./opencv_test_imgproc --gtest_filter=OCL_ImageProc/Filter2D.Mat/482

Signed-off-by: Ruiling Song <286a174c1339c6eff91abc41c3a1012c95030c95@intel.com>
Reviewed-by: Zhigang Gong  <e04a7b9b70b1e4c6318cf117dcd1a9056e14b97a@linux.intel.com>

zhenyw/beignet,wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet,freedesktop-unofficial-mirror/beignet,zhenyw/beignet,zhenyw/beignet,wdv4758h/beignet,freedesktop-unofficial-mirror/beignet,freedesktop-unofficial-mirror/beignet,freedesktop-unofficial-mirror/beignet,zhenyw/beignet,zhenyw/beignet,wdv4758h/beignet