KVM: fix addr type for KVM_IOEVENTFD

The @addr here is a guest physical address and can easily be bigger
than 4G.

This changes uint32_t to hwaddr.

Cc: qemu-stable@nongnu.org
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>