anv/state: Factor out surface state calculation from genX_image_view_init.

anv/state: Factor out surface state calculation from genX_image_view_init.

Some fields of the surface state template were dependent on the
surface type, which is dependent on the usage of the image view, which
wasn't known until the bottom of the function after the template had
been constructed.  This caused failures in all image load/store CTS
tests using cubemaps.  Refactor the surface state calculation into a
function that is called once for each required usage.