IB/hfi1: class_name_user() should be static

Fixes the following sparse warning:
  drivers/staging/rdma/hfi1/device.c:127:12:
  warning: symbol 'class_name_user' was not declared. Should it be static?
Signed-off-by: Geliang Tang <geliangtang@163.com>
Acked-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rdma/hfi1/device.c

@@ -124,7 +124,7 @@ static char *hfi1_devnode(struct device *dev, umode_t *mode)
 }
 
 static const char *hfi1_class_name_user = "hfi1_user";
-const char *class_name_user(void)
+static const char *class_name_user(void)
 {
 	return hfi1_class_name_user;
 }