simd4x4f: Fix the 2D transformation check
simd4x4f: Fix the 2D transformation check

We need to check that the z and w components of the first, second, and
fourth row vectors are an identity, as well as the whole third vector.

Using a channel access and a whole vector comparison is also cheaper
than do a comparison after a transpose.

ebassi/graphene,ebassi/graphene,criptych/graphene,criptych/graphene,criptych/graphene,criptych/graphene