generic_cartesian: Fixed kinematics coefficients calculation

For non-idex setups the calculation was returning incorrect results.

Signed-off-by: Dmitry Butyugin <dmbutyugin@google.com>

klippy/kinematics/generic_cartesian.py

@@ -161,7 +161,8 @@ def _get_kinematics_coeffs(self):
         matr = {s.get_name() : list(s.get_kin_coeffs()) for s in self.steppers}
         offs = {s.get_name() : [0.] * 3 for s in self.steppers}
         if self.dc_module is None:
-            return matr, offs
+            return [matr[s.get_name()] for s in self.steppers], \
+                    [0. for s in self.steppers]
         axes = [dc.get_axis() for dc in self.dc_carriages]
         orig_matr = copy.deepcopy(matr)
         for dc in self.dc_carriages: