libvhost-user: fix -Waddress-of-packed-member

/home/elmarco/src/qemu/contrib/libvhost-user/libvhost-user.c: In function ‘vu_set_mem_table_exec_postcopy’:
/home/elmarco/src/qemu/contrib/libvhost-user/libvhost-user.c:546:31: warning: taking address of packed member of ‘struct VhostUserMsg’ may result in an unaligned pointer value [-Waddress-of-packed-member]
  546 |     VhostUserMemory *memory = &vmsg->payload.memory;
      |                               ^~~~~~~~~~~~~~~~~~~~~
/home/elmarco/src/qemu/contrib/libvhost-user/libvhost-user.c: In function ‘vu_set_mem_table_exec’:
/home/elmarco/src/qemu/contrib/libvhost-user/libvhost-user.c:688:31: warning: taking address of packed member of ‘struct VhostUserMsg’ may result in an unaligned pointer value [-Waddress-of-packed-member]
  688 |     VhostUserMemory *memory = &vmsg->payload.memory;
      |                               ^~~~~~~~~~~~~~~~~~~~~
/home/elmarco/src/qemu/contrib/libvhost-user/libvhost-user.c: In function ‘vu_set_vring_addr_exec’:
/home/elmarco/src/qemu/contrib/libvhost-user/libvhost-user.c:817:36: warning: taking address of packed member of ‘struct VhostUserMsg’ may result in an unaligned pointer value [-Waddress-of-packed-member]
  817 |     struct vhost_vring_addr *vra = &vmsg->payload.addr;
      |                                    ^~~~~~~~~~~~~~~~~~~

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20190503130034.24916-2-marcandre.lureau@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>