net/bnxt: fix VLAN add when port is stopped

net/bnxt: fix VLAN add when port is stopped

Driver destroys the vnic when the port is brought down.
When user tries to add a vlan when port is stopped, driver
issues HWRM command to FW with invalid vnic_id and it fails.

Fixed to return an error while setting vlan when port is
not started.

Fixes: b4e190d55c25 ("net/bnxt: fix MAC/VLAN filter allocation")
Cc: stable@dpdk.org
Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>