bnxt: move bp->switch_id initialization to PF probe

Currently the switch_id is being only initialized when switching eswitch
mode from "legacy" to "switchdev". However, nothing prevents the id to
be initialized from the very beginning. Physical ports can show it even
in "legacy" mode.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>