KVM: x86/mmu: Directly "destroy" PTE list when recycling rmaps

Use pte_list_destroy() directly when recycling rmaps instead of bouncing
through kvm_unmap_rmapp() and kvm_zap_rmapp().  Calling kvm_unmap_rmapp()
is unnecessary and odd as it requires passing dummy parameters; passing
NULL for @slot when __rmap_add() already has a valid slot is especially
weird and confusing.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220715224226.3749507-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>