rhashtable: remove duplicated include from rhashtable.c

Remove duplicated include.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

lib/rhashtable.c

@@ -28,7 +28,6 @@
 #include <linux/rhashtable.h>
 #include <linux/err.h>
 #include <linux/export.h>
-#include <linux/rhashtable.h>
 
 #define HASH_DEFAULT_SIZE	64UL
 #define HASH_MIN_SIZE		4U