KVM: x86/mmu: kvm_faultin_pfn has to return false if pfh is returned

KVM: x86/mmu: kvm_faultin_pfn has to return false if pfh is returned

This looks like a typo in 8f32d5e563cb. This change didn't intend to do
any functional changes.

The problem was caught by gVisor tests.

Fixes: 8f32d5e563cb ("KVM: x86/mmu: allow kvm_faultin_pfn to return page fault handling code")
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Message-Id: <20211015163221.472508-1-avagin@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>