i965: Reorder workaround flags computation.

i965: Reorder workaround flags computation.

Vertex processing workaround flags can be split into
array and current vertex attributes. By that we
can use specific access functions for these different
vertex attribute kinds. This finally obsoletes
some access functions that I introduced last winter
for a smooth transition.

v2: Style fixes.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/308>