isl_union_*_coalesce_entry: use "PART" type instead of "PW" type
isl_union_*_coalesce_entry: use "PART" type instead of "PW" type

Even though in practice the two are always the same,
isl_union_templ.c is supposed to only reference "PART".

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

inducer/isl-mirror,BenzoSM/isl,nicolasvasilache/isl,KangDroidSMProject/ISL,inducer/isl-mirror,UBERTC/isl,nicolasvasilache/isl,inducer/isl-mirror,PollyLabs/isl,nicolasvasilache/isl,tobig/isl,Distrotech/isl,UBERTC/isl,Meinersbur/isl,KangDroidSMProject/ISL,Meinersbur/isl,PollyLabs/isl,Distrotech/isl,Meinersbur/isl,KangDroidSMProject/ISL,BenzoSM/isl,tobig/isl,Distrotech/isl,UBERTC/isl,PollyLabs/isl,inducer/isl-mirror,PollyLabs/isl,BenzoSM/isl,BenzoSM/isl,KangDroidSMProject/ISL,BenzoSM/isl,nicolasvasilache/isl,nicolasvasilache/isl,Distrotech/isl,PollyLabs/isl,tobig/isl,UBERTC/isl,Meinersbur/isl,Distrotech/isl,tobig/isl,KangDroidSMProject/ISL,inducer/isl-mirror