hwrng: imx-rngc - make symbol imx_rngc_pm_ops static

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: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/imx-rngc.c

@@ -300,7 +300,7 @@ static int __maybe_unused imx_rngc_resume(struct device *dev)
 	return 0;
 }
 
-SIMPLE_DEV_PM_OPS(imx_rngc_pm_ops, imx_rngc_suspend, imx_rngc_resume);
+static SIMPLE_DEV_PM_OPS(imx_rngc_pm_ops, imx_rngc_suspend, imx_rngc_resume);
 
 static const struct of_device_id imx_rngc_dt_ids[] = {
 	{ .compatible = "fsl,imx25-rngb", .data = NULL, },