net/bnxt: fix checking VNIC in shutdown path

net/bnxt: fix checking VNIC in shutdown path

Add a couple of NULL pointer checks in bnxt_free_all_filters()
and bnxt_free_vnics() respectively to guard against certain error
injection/recovery scenarios where it was found that the application
was crashing with the bp->vnic_info pointer being NULL.

Fixes: 51fafb89a9a0 ("net/bnxt: get rid of ff pools and use VNIC info array")
Cc: stable@dpdk.org
Signed-off-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>