Emit vector mulitply and accumulate instructions for x86.

This patch adds a new cpu vaiant named kabylake and performs
instruction simplification to generate VectorMulitplyAccumulate.

Test: ./test.py --host --64

Change-Id: Ie6cc882dadf1322dd4d3ae49bfdb600b0c447765
Signed-off-by: Gupta Kumar, Sanjiv <sanjiv.kumar.gupta@intel.com>