* enable mixed read-width / write-width ports in SDP mode
* fix NO_CHANGE and WRITE_THROUGH behavior during read access
* remove redundant zero-initialization
* set A/B_WE bit during map (gatemate_bramopt pass could be removed later)
* differentiate "upper" and "lower" initialization for cascade mode
* remove unused techmap models in `map_regs.v`
* replace RAM initilization loops with 320-bit-writes
* add script to test targets in top-level Makefile
* remove `MAXWIDTH` parameter and treat both vector widths individually in `mult_map.v`
* iterate over all modules in `gatemate_bramopt` pass