[placer1] Fix require_legal polarity
[placer1] Fix require_legal polarity

YosysHQ/nextpnr,YosysHQ/nextpnr,SymbiFlow/nextpnr,SymbiFlow/nextpnr,SymbiFlow/nextpnr,YosysHQ/nextpnr,YosysHQ/nextpnr,SymbiFlow/nextpnr