netfilter: ebt_stp: Remove unused macro BPDU_TYPE_TCN

BPDU_TYPE_TCN is never used after it was introduced.
So better to remove it.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/bridge/netfilter/ebt_stp.c

@@ -15,7 +15,6 @@
 #include <linux/netfilter_bridge/ebt_stp.h>
 
 #define BPDU_TYPE_CONFIG 0
-#define BPDU_TYPE_TCN 0x80
 
 struct stp_header {
 	u8 dsap;