Modify sunvnet common code and data structures to be compatible
  with both sunvnet and ldmvsw drivers.

  Details:

  Sunvnet operates on "vnet-port" nodes which appear in the Machine
  Description (MD) in a guest domain. Ldmvsw operates on "vsw-port"
  nodes which appear in the MD of a service domain.

  A difference between the sunvnet driver and the ldmvsw driver is
  the sunvnet driver creates a network interface (i.e. a struct net_device)
  for every vnet-port *parent* "network" node. Several vnet-ports may appear
  under this common parent network node - each corresponding to a common parent
  network interface.  Conversely, since bridge/vswitch software will need
  to interface with every vsw-port in a system, the ldmvsw driver creates
  a network interface (i.e. a struct net_device) for every vsw-port - not
  every parent node as with sunvnet.  This difference required some special
  handling in the common code as explained below.

  There are 2 key data structures used by the sunvnet and ldmvsw drivers
  (which are now found in sunvnet_common.h):

  1. struct vnet_port
     This structure represents a vnet-port node in sunvnet and a vsw-port
     in the ldmvsw driver.

  2. struct vnet
     This structure represents a parent "network" node in sunvnet and a parent
     "virtual-network-switch" node in ldmvsw.

  Since the sunvnet driver allocates a net_device for every parent "network"
  node, a net_device member appears in the struct vnet. Since the ldmvsw
  driver allocates a net_device for every port, a net_device member was
  added to the vnet_port. The common code distinguishes which structure
  net_device member to use by checking a 'vsw' bit that was added to the
  vnet_port structure. See the VNET_PORT_TO_NET_DEVICE() marco in
  sunvnet_common.h.

  The netdev_priv() in sunvnet is allocated as a vnet. The netdev_priv()
  in ldmvsw is a vnet_port. Therefore, any place in the common code
  where a netdev_priv() call was made, a wrapper function was implemented
  in each driver to first get the vnet and/or vnet_port (in a driver
  specific way) and pass them as newly added parameters to the common
  functions (see wrapper funcs: vnet_set_rx_mode() and vnet_poll_controller()).
  Since these wrapper functions call __tx_port_find(), __tx_port_find() was
  moved from the common code back into sunvnet.c. Note - ldmvsw.c does not
  require this function.

  These changes also required that port_is_up() be made
  into a common function and thus it was given a _common suffix and
  exported like the other common functions.

  A wrapper function was also added for vnet_start_xmit_common() to pass a
  driver-specific function arg to return the port associated with a given
  struct sk_buff and struct net_device. This was required because
  vnet_start_xmit_common() grabs a lock prior to getting the associated
  port. Using a function pointer arg allowed the code to work unchanged
  without risking changes to the non-trivial locking logic in
  vnet_start_xmit_common().
Signed-off-by: Aaron Young <aaron.young@oracle.com>
Signed-off-by: Rashmi Narasimhan <rashmi.narasimhan@oracle.com>
Reviewed-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Reviewed-by: Alexandre Chartre <Alexandre.Chartre@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>