add the reduced self loop node detection.
add the reduced self loop node detection.

if the self loop node is reduced, the llvm loop info couldn't detect
such kind of self loops, handle it by checking whether the compacted
node has a successor pointed to itself.

v2: differentiate the compacted node from basic node to make the logic
clearer, comments the while node as it is not enabled now.

Signed-off-by: Luo Xionghu <c3dafbeb50547b880155fb36e6f40d38b44f6611@intel.com>
Reviewed-by: Zhigang Gong <e04a7b9b70b1e4c6318cf117dcd1a9056e14b97a@linux.intel.com>

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