Remove matrix type field

In !1015 (merged) we're replacing this loosely tracked (reversing a rotation can't revert the type field to its pre-rotated value) with matrix inspection. This mostly removes the need to track the type at all, but there are still some places that use it (specifically weston_view_update_transform_enable().

It should be possible to replace the usage of matrix type there too, and remove matrix type entirely.