don't merge serial blocks with barrier.
don't merge serial blocks with barrier.

this could fix the piglit and opencv fail on IVB_x86 platform.
1) opencv_test_core/OCL_Arithm/CountNonZero
2) opencv_test_core/OCL_Arithm/MeanStdDev
3) piglit case program/execute/atomic_cmpxchg-local.
v2: update comments: As our barrier implementation doen't support
structured barrier operation, exclude all the barrier blocks from
serialPatternMatch.

Signed-off-by: Luo Xionghu <c3dafbeb50547b880155fb36e6f40d38b44f6611@intel.com>
Reviewed-by: "Song, Ruiling" <286a174c1339c6eff91abc41c3a1012c95030c95@intel.com>

wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet