netfilter: nf_conntrack_ipv6: delete the redundant macro definitions

The following three macro definitions are never used, so delete them.
Signed-off-by: NShan Wei <shanwei@cn.fujitsu.com>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NPatrick McHardy <kaber@trash.net>

net/ipv6/netfilter/nf_conntrack_reasm.c

@@ -45,9 +45,6 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 
-#define NF_CT_FRAG6_HIGH_THRESH 262144 /* == 256*1024 */
-#define NF_CT_FRAG6_LOW_THRESH 196608  /* == 192*1024 */
-#define NF_CT_FRAG6_TIMEOUT IPV6_FRAG_TIMEOUT
 
 struct nf_ct_frag6_skb_cb
 {