tcp_cubic: use memset and offsetof init

In bictcp_reset(), use memset and offsetof instead of = 0.
Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
Link: https://lore.kernel.org/r/1610597696-128610-1-git-send-email-yejune.deng@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/tcp_cubic.c

@@ -104,16 +104,7 @@ struct bictcp {
 
 static inline void bictcp_reset(struct bictcp *ca)
 {
-	ca->cnt = 0;
-	ca->last_max_cwnd = 0;
-	ca->last_cwnd = 0;
-	ca->last_time = 0;
-	ca->bic_origin_point = 0;
-	ca->bic_K = 0;
-	ca->delay_min = 0;
-	ca->epoch_start = 0;
-	ca->ack_cnt = 0;
-	ca->tcp_cwnd = 0;
+	memset(ca, 0, offsetof(struct bictcp, unused));
 	ca->found = 0;
 }