KVM: x86/mmu: fix comment about mmu_unsync_pages_lock

Fix the comment about what can and cannot happen when mmu_unsync_pages_lock
is not help.  The comment correctly mentions "clearing sp->unsync", but then
it talks about unsync going from 0 to 1.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20231125083400.1399197-5-pbonzini@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: bonzini

arch/x86/kvm/mmu/mmu.c

@@ -2850,9 +2850,9 @@ int mmu_try_to_unsync_pages(struct kvm *kvm, const struct kvm_memory_slot *slot,
 			/*
 			 * Recheck after taking the spinlock, a different vCPU
 			 * may have since marked the page unsync.  A false
-			 * positive on the unprotected check above is not
+			 * negative on the unprotected check above is not
 			 * possible as clearing sp->unsync _must_ hold mmu_lock
-			 * for write, i.e. unsync cannot transition from 0->1
+			 * for write, i.e. unsync cannot transition from 1->0
 			 * while this CPU holds mmu_lock for read (or write).
 			 */
 			if (READ_ONCE(sp->unsync))