[OE-core] Fix for the APIC hangs in qemux86-64

[Richard Purdie]

Hi Bruce,

https://bugzilla.yoctoproject.org/show_bug.cgi?id=12301

We've root caused the hangs we're seeing in qemux86-64 on our
autobuilder workers. We've identified a commit on 4.15-rc3 which fixes
the issue but backporting it to the autobuilder's host kernels will be
a pain.

As a workaround I'd like to enable x2apic on qemux86-64. Since that
works via MSRs it avoids the problem. 

Would it be a big issue to set CONFIG_X86_X2APIC=y for qemux86-64?

Cheers,

Richard