Currently, mlxsw has several shortcomings with regards to RIF handling due
to PVID changes:

- In order to cause RIF for a bridge device to be created, the user is
  expected first to set PVID, then to add an IP address. The reverse
  ordering is disallowed, which is not very user-friendly.

- When such bridge gets a VLAN upper whose VID was the same as the existing
  PVID, and this VLAN netdevice gets an IP address, a RIF is created for
  this netdevice. The new RIF is then assigned to the 802.1Q FID for the
  given VID. This results in a working configuration. However, then, when
  the VLAN netdevice is removed again, the RIF for the bridge itself is
  never reassociated to the VLAN.

- PVID cannot be changed once the bridge has uppers. Presumably this is
  because the driver does not manage RIFs properly in face of PVID changes.
  However, as the previous point shows, it is still possible to get into
  invalid configurations.

In this patch, add the logic necessary for creation of a RIF as a result of
PVID change. Moreover, when a VLAN upper is created whose VID matches lower
PVID, do not create RIF for this netdevice.

These changes obviate the need for ordering of IP address additions and
PVID configuration, so stop forbidding addition of an IP address to a
PVID-less bridge. Instead, bail out quietly. Also stop preventing PVID
changes when the bridge has uppers.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Danielle Ratson <danieller@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>