KVM_GUEST adds a 1 MB array to the kernel (kvm_tmp) which grew
my kernel enough to cause it to fail to boot.

Dynamically allocating or reducing the size of this array is a
good idea, but in the meantime I think it makes sense to make
KVM_GUEST default to n in order to minimise surprises.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>