Improve diode LEF files.

 * Add `USE` and `SHAPE` properties.
 * Remove `CORE` class.
 * Fix layer for power pins.

Fixes https://github.com/google/skywater-pdk/issues/141.

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>
tree: 0ccdf627b909b0cc5fcbf6d98b8900d012823325
  1. cells/
  2. models/
  3. tech/
  4. timing/
  5. .gitignore
  6. LICENSE
  7. README.rst