Fix the name of nwell and rdl generic resistors.

Convert `mrnw` to `sky130_fd_pr__res_generic_nw`.
Convert `mrrdl` to `sky130_fd_pr__res_generic_r1`.

Fixes https://github.com/google/skywater-pdk/issues/168

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>