Corrected the "short" model which is actually being called as a
subcircuit, not a resistor, from the extraction in magic. Also added
a new custom file "diode.spice" which does the same thing for the
diodes, which are defined as low-level diode types but are extracted
from magic as a subcircuit.
diff --git a/sky130/custom/models/diode.spice b/sky130/custom/models/diode.spice
new file mode 100644
index 0000000..81bee35
--- /dev/null
+++ b/sky130/custom/models/diode.spice
@@ -0,0 +1,9 @@
+* For diodes called as a subcircuit
+* (backwards compatible with earlier PDK version)
+.subckt sky130_fd_pr__diode_pw2nd N P a=0 p=0
+D0 N P sky130_fd_pr__diode_pw2nd_05v5 area=a
+.ends
+* (corresponds to current PDK)
+.subckt sky130_fd_pr__diode_pw2nd_05v5 N P area=0
+D0 N P sky130_fd_pr__diode_pw2nd_05v5 area=area
+.ends
