6lowpan: fix assignment of peer_addr

6lowpan: fix assignment of peer_addr

The data from peer->chan->dst is not being copied to peer_addr, the
current code just updates the pointer and not the contents of what
it points to.  Fix this with the intended assignment.

Detected by CoverityScan, CID#1422111 ("Parse warning
(PW.PARAM_SET_BUT_NOT_USED)")

Fixes: fb6f2f606ce8 ("6lowpan: Fix IID format for Bluetooth")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>