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 <[e-mail]>
Signed-off-by: Wang Hai <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/bridge/netfilter/ebt_stp.c

···
 #include <linux/netfilter_bridge/ebt_stp.h>
 
 #define BPDU_TYPE_CONFIG 0
-#define BPDU_TYPE_TCN 0x80
 
 struct stp_header {
 	u8 dsap;