busybox

networking/libiproute: use <linux/if_packet.h> instead of <net/if_packet.h>

The musl C library doesn't provide the <net/if_packet.h> since the
corresponding kernel headers <linux/if_packet.h> already provides the
necessary definitions. Replacing <net/if_packet.h> by
<linux/if_packet.h> also removes the need to include
<netpacket/packet.h>

This commit fixes the build of iplink with the musl C library.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[Gustavo: update for busybox 1.22.0]