The extruder check_move() code will permit moves with huge extrusion
ratios if the amount extruded is tiny. (Some slicers emit these silly
moves - they are allowed because they are harmless.) Unfortunately,
the pressure advance code did not handle the huge extrusion ratios -
it would result in a massive, near instantaneous, extruder move in an
attempt to build pressure in the extruder. Catch this case and limit
the impact to the pressure advance code.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>