net: skbuff: drop the linux/sched/clock.h include

It used to be necessary for skb_mstamp_* static inlines,
but those are gone since we moved to usec timestamps in
TCP, in 2017.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -29,7 +29,6 @@
 #include <linux/dma-mapping.h>
 #include <linux/netdev_features.h>
 #include <linux/sched.h>
-#include <linux/sched/clock.h>
 #include <net/flow_dissector.h>
 #include <linux/splice.h>
 #include <linux/in6.h>