wall-spy: Document that the command works with TAP and Intel devices
wall-spy: Document that the command works with TAP and Intel devices

The README for the SnabbWall's "wall spy" command did not reflect the
fact that the tool supports pulling packets from TAP and Intel devices.

snabbco/snabb,eugeneia/snabb,eugeneia/snabb,mixflowtech/logsensor,snabbco/snabb,alexandergall/snabbswitch,Igalia/snabb,Igalia/snabb,SnabbCo/snabbswitch,heryii/snabb,eugeneia/snabbswitch,Igalia/snabb,snabbco/snabb,mixflowtech/logsensor,heryii/snabb,dpino/snabbswitch,dpino/snabbswitch,eugeneia/snabb,eugeneia/snabbswitch,snabbco/snabb,Igalia/snabbswitch,dpino/snabb,alexandergall/snabbswitch,Igalia/snabbswitch,snabbco/snabb,Igalia/snabb,snabbco/snabb,alexandergall/snabbswitch,eugeneia/snabb,alexandergall/snabbswitch,dpino/snabb,Igalia/snabb,Igalia/snabbswitch,heryii/snabb,dpino/snabb,eugeneia/snabbswitch,heryii/snabb,dpino/snabb,Igalia/snabb,Igalia/snabb,dpino/snabbswitch,eugeneia/snabb,dpino/snabb,Igalia/snabbswitch,mixflowtech/logsensor,eugeneia/snabbswitch,alexandergall/snabbswitch,snabbco/snabb,eugeneia/snabb,SnabbCo/snabbswitch,dpino/snabb,alexandergall/snabbswitch,Igalia/snabbswitch,mixflowtech/logsensor,alexandergall/snabbswitch,alexandergall/snabbswitch,eugeneia/snabb,heryii/snabb,mixflowtech/logsensor,eugeneia/snabb,dpino/snabbswitch,SnabbCo/snabbswitch,Igalia/snabb,SnabbCo/snabbswitch,snabbco/snabb,dpino/snabb,heryii/snabb