mlxsw: spectrum_switchdev: Don't warn about valid situations

Some operations in the bridge driver such as MDB deletion are preformed
in an atomic context and thus deferred to a process context by the
switchdev infrastructure.

Therefore, by the time the operation is performed by the underlying
device driver it's possible the bridge port context is already gone.
This is especially true for removal flows, but theoretically can also be
invoked during addition.

Remove the warnings in such situations and return normally.

Fixes: c57529e1 ("mlxsw: spectrum: Replace vPorts with Port-VLAN")
Fixes: 3922285d

 ("net: bridge: Add support for offloading port attributes")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>