bnxt_en: export a common switchdev PARENT_ID for all reps of an adapter

Currently the driver exports different switchdev PARENT_IDs for
representors belonging to different SR-IOV PF-pools of an adapter.
This is not correct as the adapter can switch across all vports
of an adapter. This patch fixes this by exporting a common switchdev
PARENT_ID for all reps of an adapter. The PCIE DSN is used as the id.

Signed-off-by: Sathya Perla <sathya.perla@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>