Fixes the following sparse warnings:

drivers/char/hw_random/imx-rngc.c:303:1: warning:
 symbol 'imx_rngc_pm_ops' was not declared. Should it be static?
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: NMartin Kaiser <martin@kaiser.cx>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>