lguest: update lazy mmu changes to match lguest's use of kvm hypercalls

Duplicate hcall -> kvm_hypercall0 convertion from "lguest: use KVM
hypercalls".

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Matias Zabaljauregui <zabaljauregui at gmail.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>