PowerPC - Asset failure on CPUs that lack L2 cache

[techflashYT]

I get the following assertion failure on CPUs that lack L2 cache - specifically on PPC (can't replicate on anything else).

cpufetch: src/common/cpu.c:136: get_str_l2: Assertion `cach->L2->exists' failed.
Aborted (core dumped)

I can replicate this on a "Broadway" (Nintendo Wii CPU - Modified PowerPC 750CL), as well as on a QEMU Virtual Machine running on a POWER9.
I have some code that can fix this, if you want it, however you've noted that you do not accept pull requests, and prefer to work on it yourself, so I have not provided it here. Let me know if you would like it.

I would be happy to try out any changes on the same hardware, if you want, as well.