nfsd: remove duplicated include from filecache.c

Remove duplicated include.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/filecache.c

@@ -6,7 +6,6 @@
 
 #include <linux/hash.h>
 #include <linux/slab.h>
-#include <linux/hash.h>
 #include <linux/file.h>
 #include <linux/sched.h>
 #include <linux/list_lru.h>