rhashtable: using ERR_PTR requires linux/err.h

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

lib/rhashtable.c

@@ -23,6 +23,7 @@
 #include <linux/jhash.h>
 #include <linux/random.h>
 #include <linux/rhashtable.h>
+#include <linux/err.h>
 
 #define HASH_DEFAULT_SIZE	64UL
 #define HASH_MIN_SIZE		4UL