glsl: add AoA support to subroutines

glsl: add AoA support to subroutines

process_parameters() will now be called earlier because we need
actual_parameters processed earlier so we can use it with
match_subroutine_by_name() to get the subroutine variable, we need
to do this inside the recursive function generate_array_index() because
we can't create the ir_dereference_array() until we have gotten to the
outermost array.

For the remainder of the array dimensions the type doesn't matter so we
can just use the existing _mesa_ast_array_index_to_hir() function to
process the ast.

Reviewed-by: Dave Airlie <airlied@redhat.com>