staging: dpaa2-ethsw: verify the nofifier block

staging: dpaa2-ethsw: verify the nofifier block

Since now we have a notifier block for each DPSW instance probed, we
have to also check that the netdev is indeed connected to the notifier
received. Without this, we end up with the same switchdev callback being
executed multiple times (because it would be received by all notifier
blocks, not just the one intended to).
Also, move the function higher in the source file because it will be
used in later patches from multiple places.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20200721091919.20394-2-ioana.ciornei@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>