isl_pw_templ.c: move isl_pw_*_sort_unique up
isl_pw_templ.c: move isl_pw_*_sort_unique up

This function will be used from isl_pw_*_gist_fn in the next commit.

Signed-off-by: Sven Verdoolaege <dd860110a62b19214c4ee03aec0abffecb4e86b8@cerebras.net>

Meinersbur/isl,Meinersbur/isl,Meinersbur/isl,Meinersbur/isl