config: move x86 kvm_guest.config to a common location

kvm_guest.config is useful for KVM guests on other arches, and nothing
in it appears to be x86 specific, so just move the whole file. Kbuild
will find it in either location.

Signed-off-by: Rob Herring <[email protected]>
Cc: Christoffer Dall <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: "Radim Krčmář" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Acked-by: Christoffer Dall <[email protected]>
Signed-off-by: Radim Krčmář <[email protected]>