get_real_device() has 5 parameters with the last 4 is contained in the first
structure.

This patch removes the last 4 parameters and directly use them from the first
parameter.
Acked-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NWei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>