net/bnxt: fix build
net/bnxt: fix build

For gcc (GCC) 4.8.3 20140911 (Red Hat 4.8.3-7),
As of 5ef3b79fdfe6f, compilation of DPDK fails with the following
ERROR MESSAGE:
"bnxt_filter.c:960:117: error: ‘vnic’ may be used uninitialized in this
function [-Werror=maybe-uninitialized]".

Resolve this by initializing 'vnic' to NULL;

Fixes: 5ef3b79fdfe6 ("net/bnxt: support flow filter ops")

Signed-off-by: Mark Kavanagh <e707d542dc7a54f2c5fa7322607639c7566e5802@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk