gpl: Fix a few documentation issues
gpl: Fix a few documentation issues

- Move all options under the Tuning Parameters heading
- Remove -grid_count, the option is -bin_grid_count and it is documented
  further down
- -init_wire_length_coef should be -init_wirelength_coef

Signed-off-by: Anton Blanchard <14deb5e5e417133e888bf47bb6a3555c9bb7d81c@linux.ibm.com>

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