Replacing `is` with `==` for the dtype check.

>>> a = np.ndarray([1,1]).astype(np.half)
>>> a
array([[0.007812]], dtype=float16)
>>> a.dtype
dtype('float16')
>>> a.dtype == np.half
True
>>> a.dtype == np.float16
True
>>> a.dtype is np.float16
False

Checking with `is` leads to inconsistency in checking.

Reviewed By: silvas

Differential Revision: https://reviews.llvm.org/D139121