Fix the following sparse warnings:

  drivers/edac/fsl_ddr_edac.c:148:1: warning:
   symbol 'dev_attr_inject_data_hi' was not declared. Should it be static?
  drivers/edac/fsl_ddr_edac.c:150:1: warning:
   symbol 'dev_attr_inject_data_lo' was not declared. Should it be static?
  drivers/edac/fsl_ddr_edac.c:152:1: warning:
   symbol 'dev_attr_inject_ctrl' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/20170209150424.15124-1-weiyj.lk@gmail.comSigned-off-by: Borislav Petkov <bp@suse.de>