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>