Add support for AMD mobile Zen 4 (Phoenix)

[kronbichler]

This PR adds (experimental) support for the AMD Zen 4 mobile architecture (codenamed Phoenix):

CPU name:	AMD Ryzen 7 PRO 7840U w/ Radeon 780M Graphics  
CPU type:	AMD K19 (Zen4) architecture
CPU clock:	3.29 GHz

This is just a very rough setting to get the architecture running (looking at what ZEN3_RYZEN2 did), I am happy to add additional settings if I get some guidance, as I see several warnings in some of the other Zen 4 groups.

[TomTheBear]

Many thanks for the PR. I checked AMD Documentation Hub but cannot find the suitable PPR for the micro-arch. So, there is not much more you could do at the moment. There are some locations, where the new ZEN4_RYZEN2 should be added (1, 2) for more features. Maybe this reduces the warnings. If you post the remaining warnings here, I could help you sorting them out.

General documentation how to add new x86 architectures: https://github.com/RRZE-HPC/likwid/wiki/AddX86Support

[kronbichler]

Thanks for fixing up my initial attempt; I lost track of this as I had my local version running, I apologize for the missing reply. Anyway, this update is of course highly appreciated!