drt: fix backwards x/y in gcell grid report
drt: fix backwards x/y in gcell grid report

Signed-off-by: Matt Liberty <33dc4132df24948aa98d8f0631d72d09479d92ab@gmail.com>

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