ice40: Add global network output support for LFOSC/HFOSC
ice40: Add global network output support for LFOSC/HFOSC

Signed-off-by: Sylvain Munaut <349f318521b45672c77207abf1a5ed60eb011db1@246tNt.com>

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