e1000e: Include clocksource.h to get CLOCKSOURCE_MASK.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index e14fd85..2537d36a 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -43,6 +43,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/aer.h>
 #include <linux/prefetch.h>
+#include <linux/clocksource.h>
 
 #include "e1000.h"