net/codel: Add missing #include <linux/prefetch.h>

m68k allmodconfig:

net/sched/sch_codel.c: In function ‘dequeue’:
net/sched/sch_codel.c:70: error: implicit declaration of function ‘prefetch’
make[1]: *** [net/sched/sch_codel.o] Error 1

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_codel.c

@@ -46,6 +46,7 @@
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/skbuff.h>
+#include <linux/prefetch.h>
 #include <net/pkt_sched.h>
 #include <net/codel.h>