amt: remove duplicate include in amt.c

'net/protocol.h' included in 'drivers/net/amt.c' is duplicated.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Zhang Mingyu <zhang.mingyu@zte.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/amt.c

@@ -22,7 +22,6 @@
 #include <linux/security.h>
 #include <net/gro_cells.h>
 #include <net/ipv6.h>
-#include <net/protocol.h>
 #include <net/if_inet6.h>
 #include <net/ndisc.h>
 #include <net/addrconf.h>