bnxt_en: fix dst/src fid for vxlan encap/decap actions

For flows that involve a vxlan encap action, the vxlan sock
interface may be specified as the outgoing interface. The driver
must resolve the outgoing PF interface used by this socket and
use the dst_fid of the PF in the hwrm_cfa_encap_record_alloc cmd.

Similarily for flows that have a vxlan decap action, the
fid of the incoming PF interface must be used as the src_fid in
the hwrm_cfa_decap_filter_alloc cmd.

Fixes: 8c95f773

 ("bnxt_en: add support for Flower based vxlan encap/decap offload")
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>