uapi: netfilter_arp: use __u8 instead of u_int8_t

Similarly, the u_int8_t type is non-standard and not defined. Change
it to use __u8 like the rest of the netfilter headers.

Signed-off-by: Mike Frysinger <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/uapi/linux/netfilter_arp/arpt_mangle.h

···
 	union {
 		struct in_addr tgt_ip;
 	} u_t;
-	u_int8_t flags;
+	__u8 flags;
 	int target;
 };