net/bnxt: use common function to free VNIC resource

net/bnxt: use common function to free VNIC resource

Use the function bnxt_vnic_destroy() to destroy VNIC resources
and thereby eliminate few duplicate code.

Fixes: 8d0a244b40b2 ("net/bnxt: cleanup VNIC after flow validate")
Fixes: 49d0709b257f ("net/bnxt: delete and flush L2 filters cleanly")
Cc: stable@dpdk.org
Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>