mmc: sdhci-esdhc-imx: Assign system PM ops within #ifdef CONFIG_PM_SLEEP

The system PM callbacks isn't used unless CONFIG_PM_SLEEP is set, thus it
triggers a compiler warning about unused functions. Avoid this by changing
from CONFIG_PM to CONFIG_PM_SLEEP.
Reported-by: Arnd Bergmann <arnd@arndb.de>
Fixes: b70d0b3b5b29 ("mmc: sdhci-esdhc-imx: add esdhc specific suspend resume callback")
Cc: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Dong Aisheng <aisheng.dong@nxp.com>

drivers/mmc/host/sdhci-esdhc-imx.c

@@ -1293,7 +1293,7 @@ static int sdhci_esdhc_imx_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 static int sdhci_esdhc_suspend(struct device *dev)
 {
 	return sdhci_pltfm_suspend(dev);
@@ -1308,7 +1308,9 @@ static int sdhci_esdhc_resume(struct device *dev)
 
 	return sdhci_pltfm_resume(dev);
 }
+#endif
 
+#ifdef CONFIG_PM
 static int sdhci_esdhc_runtime_suspend(struct device *dev)
 {
 	struct sdhci_host *host = dev_get_drvdata(dev);