The idea is that you can
speed up execution if you have SSE2 instructions available, but we don't
want to break things for those that don't have them. The warning is there
to suggest that you put in the correct value

I would welcome a patch where someone ran

./util/abuild/abuild -C -a
grep -L "SSE " coreboot-builds/*/config.h
grep -L "SSE2 " coreboot-builds/*/config.h

Then added the correct values to the src/cpu/*/*/Kconfig files.

It would take some time with wikipedia.

On the other hand, since you know your CPU doesn't support SSE2, you could just mention your CPU by name, and I'll add the correct value for SSE2 to the correct file.

Thanks,
Myles