i40evf: remove redundant array comparisons to 0 checks

The checks to see if key->dst.s6_addr and key->src.s6_addr are null
pointers are redundant because these are constant size arrays and
so the checks always return true.  Fix this by removing the redundant
checks.   Also replace filter->f with vf, allowing wide lines to be
condensed and to rejoin some split wide lines.

Detected by CoverityScan, CID#1465279 ("Array compared to 0")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>