Quicklogic 'qlf_k4n8' device support in yosys

[sharmaln]

This PR merges QuickLogic 'qlf_k4n8' device in Symbiflow-yosys. This is required as a prerequisite to another PR: https://github.com/SymbiFlow/symbiflow-arch-defs/pull/2036 where this device support is added in Symbiflow-arch-defs. But CI is failing for that PR because yosys does not have this device support. So, I am adding this device support to yosys.

[kgugala]

@lnsharma can you rebase this and remove the Merge pull request #1 from lnsharma/add_qlf_k4n8_dev commit?

[litghost]

I thought we had discussed managing this as a plugin? Am I misremembering?

[kgugala]

This is a different device. This PR adds synthesis for openFPGA generated qlf_k4n8 chip (and is needed in https://github.com/SymbiFlow/symbiflow-arch-defs/pull/2036 so it can go green).

It'd be really good to have it supported. In general openFPGA also uses VPR so there may be nice overlap.

If we can get land this PR, conda builder will generate a package from it and we should be able to land arch-defs PR (this will be much faster than packing it all into a plugin, especially with techmaps etc)

[sharmaln]

@litghost , @kgugala : Still awaiting response, if this is merged then we can proceed with merging k4n8 device support in Symbiflow-arch-defs.

[litghost]

@litghost , @kgugala : Still awaiting response, if this is merged then we can proceed with merging k4n8 device support in Symbiflow-arch-defs.

I already gave my response. All of this data should be managed as a plugin, e.g. the code should be compiled into an .so (or equiv) and the data should be located in the plugins data folder.

[kgugala]

Sure, we'll pack it into a lib so we can code use this as a plugin