[fpga] connect `cptra_ss_lc_Allow_RMA_or_SCRAP_on_PPD_i` to GPIO to enable toggling in HW Model

[timothytrippel]

The Physical Presents Detection (PPD) pin in the FPGA wrapper should be connected to a GPIO to facilitate testing RMA and Scrap LC transitions on FPGA (see chipsalliance/caliptra-ss#233).