net/bnxt: check invalid VNIC in cleanup path

net/bnxt: check invalid VNIC in cleanup path

The cleanup/rollback operation post rte_eth_dev_start failure might end
up invoking an HWRM cmd even on an invalid vNIC resulting in error
messages being logged needlessly.
Fix to check for the same before issuing the HWRM cmd.

Fixes: c09f57b49c13 ("net/bnxt: add start/stop/link update operations")
Cc: stable@dpdk.org
Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>