x86: KVM guest: hypercall batching

Batch pte updates and tlb flushes in lazy MMU mode.

[avi:
 - adjust to mmu_op
 - helper for getting para_state without debug warnings]

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>