hv_netvsc: remove duplicated including of slab.h

rm the second include <linux/slab.h>
Signed-off-by: Wang Jinchao <wangjinchao@xfusion.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/rndis_filter.c

@@ -21,7 +21,6 @@
 #include <linux/rtnetlink.h>
 #include <linux/ucs2_string.h>
 #include <linux/string.h>
-#include <linux/slab.h>
 
 #include "hyperv_net.h"
 #include "netvsc_trace.h"