Yosys API change breaks .bits

[akashlevy]

In the latest version of Yosys .bits was changed to .bits(). This should eventually be reflected in the slang frontend.

[akashlevy]

Can make a quick PR for this if needed

[povik]

Thanks. I will see if there's a good way to write it in a way which will work both before and after the YosysHQ/yosys#4516 change

[povik]

Presumably fixed in 7a9960c (in the staging branch)