verilog: Fixing power pins usage in non-powerpin mode.

Previously even when `USE_POWER_PIN` was not defined, the drive strength
wrappers where still defining the power pins as ports.

Fixes https://github.com/google/skywater-pdk/issues/181

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>
tree: f95106898be151c1c074ec9cf6ce084f7fc1d0b8
  1. .gitignore
  2. LICENSE
  3. README.rst
  4. cells/
  5. models/
  6. tech/
  7. timing/