glsl: Convert piles of foreach_iter to foreach_list_safe.

glsl: Convert piles of foreach_iter to foreach_list_safe.

In these cases, we edit the list (or at least might be), so we use the
foreach_list_safe variant.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>