The kernel commit 'packet: make packet_snd fail on len smaller than l2
header' started rejecting <= 14 octet raw packet socket transmission.
This test case was testing with 14 ocets and that is now rejected by the
kernel. While this may be a kernel side issue, use one octet longer test
data for now to avoid undesired FAIL cases in hwsim tests.
Signed-off-by: Jouni Malinen <j@w1.fi>