kvm: make KVM_COALESCED_MMIO_PAGE_OFFSET public

Its value has never changed; we might as well make it part of the ABI instead
of using the return value of KVM_CHECK_EXTENSION(KVM_CAP_COALESCED_MMIO).

Because PPC does not always make MMIO available, the code has to be made
dependent on CONFIG_KVM_MMIO rather than KVM_COALESCED_MMIO_PAGE_OFFSET.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f1339a7..7e74ae4d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -403,7 +403,7 @@ struct kvm {
 	struct kvm_vm_stat stat;
 	struct kvm_arch arch;
 	refcount_t users_count;
-#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
+#ifdef CONFIG_KVM_MMIO
 	struct kvm_coalesced_mmio_ring *coalesced_mmio_ring;
 	spinlock_t ring_lock;
 	struct list_head coalesced_zones;