mmc: sdhci-pltfm: Fix linking err for sdhci-brcmstb

The implementation of sdhci_pltfm_suspend() is only available when
CONFIG_PM_SLEEP is set, which triggers a linking error:

"undefined symbol: sdhci_pltfm_suspend" when building sdhci-brcmstb.c.

Fix this by implementing the missing stubs when CONFIG_PM_SLEEP is unset.

Reported-by: Arnd Bergmann <[e-mail]>
Suggested-by: Florian Fainelli <[e-mail]>
Fixes: 5b191dcba719 ("mmc: sdhci-brcmstb: Fix mmc timeout errors on S5 suspend")
Cc: [e-mail]
Tested-By: Nicolas Schichan <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Acked-by: Florian Fainelli <[e-mail]>
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/mmc/host/sdhci-pltfm.h

···
 	return host->private;
 }
 
+extern const struct dev_pm_ops sdhci_pltfm_pmops;
+#ifdef CONFIG_PM_SLEEP
 int sdhci_pltfm_suspend(struct device *dev);
 int sdhci_pltfm_resume(struct device *dev);
-extern const struct dev_pm_ops sdhci_pltfm_pmops;
+#else
+static inline int sdhci_pltfm_suspend(struct device *dev) { return 0; }
+static inline int sdhci_pltfm_resume(struct device *dev) { return 0; }
+#endif
 
 #endif /* _DRIVERS_MMC_SDHCI_PLTFM_H */