odb: never allow SITE before UNITS in LEF
odb: never allow SITE before UNITS in LEF

Fixes The-OpenROAD-Project/OpenLane#1364

Signed-off-by: Matt Liberty <44ef1ce0ef6935daf739a0795dad249ba5322e97@eng.ucsd.edu>

The-OpenROAD-Project/OpenROAD,QuantamHD/OpenROAD,The-OpenROAD-Project/OpenROAD,QuantamHD/OpenROAD,The-OpenROAD-Project/OpenROAD,QuantamHD/OpenROAD,The-OpenROAD-Project/OpenROAD,The-OpenROAD-Project/OpenROAD,QuantamHD/OpenROAD,QuantamHD/OpenROAD