mlx4_en: remove duplicated #include

Removed duplicated #include <linux/cpumask.h> in
drivers/net/mlx4/en_main.c.

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/net/mlx4/en_main.c

@@ -35,7 +35,6 @@
 #include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/netdevice.h>
-#include <linux/cpumask.h>
 
 #include <linux/mlx4/driver.h>
 #include <linux/mlx4/device.h>