* Refactor MKL-DNN ElementwiseMul

remove manual fallback, remove format attrs
test=develop

* Refine PADDLE_ENFORCEs in eltwise_mul_op.h

test=develop

* Make ElementwiseMulOp inherit from ElementwiseOp

* Change type of simd_width to int

test=develop

* Remove Constructor extensions in ElementwiseOp and ElementwiseMulOp

test=develop

* Restore attributes

test=develop

* Fix test coverage for mkldnn eltwise mul

test=develop

* Conform to new is_run_common_broadcast API

test=develop

* Add UT for AreDimsAndFormatCorrect

test=develop