mac_len is of type unsigned, which can never be less than zero.

	mac_len = ieee802154_hdr_peek_addrs(skb, &header);
	if (mac_len < 0)
		return mac_len;

Change this to type int as ieee802154_hdr_peek_addrs() can return negative
integers, this is found by static analysis with smatch.

Fixes: 6c993779 ("ca8210: fix mac_len negative array access")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230306191824.4115839-1-harshit.m.mogalapalli@oracle.comSigned-off-by: Stefan Schmidt <stefan@datenfreihafen.org>