dpaa2-switch: move a check to the prechangeupper stage

Two different DPAA2 switch ports from two different DPSW instances
cannot be under the same bridge. Instead of checking for this
unsupported configuration in the CHANGEUPPER event, check it as early as
possible in the PRECHANGEUPPER one.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>