staging: dpaa2-ethsw: don't allow interfaces from different DPSWs to be bridged

Error out when the user tries to bridge two switch interfaces that are
from different DPSW instances. This is not supported by the hardware and
we should reflect this into what the user is aware of.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20200721091919.20394-3-ioana.ciornei@nxp.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>