netsniff-ng: check if linux-headers are v3.0 or higher

netsniff-ng uses the TP_STATUS_VLAN_VALID define, provided by the
kernel headers. This definition has been added in the kernel by commit
a3bcc23e890a6d49d6763d9eb073d711de2e0469 ("af-packet: Add flag to
distinguish VID 0 from no-vlan"), which was merged in v3.0.

Fixes:
http://autobuild.buildroot.net/results/c87/c87a440e29ae387f600cb6ecce3caaa08557f4f0/



Signed-off-by: Joris Lijssens <joris.lijssens@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>