net: stmmac: platform: fix build error with !CONFIG_PM_SLEEP

Get rid of the CONFIG_PM_SLEEP ifdefery to fix the build error
and use __maybe_unused for the suspend()/resume() hooks to avoid
build warning:

drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c:769:21:
 error: 'stmmac_runtime_suspend' undeclared here (not in a function); did you mean 'stmmac_suspend'?
  769 |  SET_RUNTIME_PM_OPS(stmmac_runtime_suspend, stmmac_runtime_resume, NULL)
      |                     ^~~~~~~~~~~~~~~~~~~~~~
./include/linux/pm.h:342:21: note: in definition of macro 'SET_RUNTIME_PM_OPS'
  342 |  .runtime_suspend = suspend_fn, \
      |                     ^~~~~~~~~~
drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c:769:45:
 error: 'stmmac_runtime_resume' undeclared here (not in a function)
  769 |  SET_RUNTIME_PM_OPS(stmmac_runtime_suspend, stmmac_runtime_resume, NULL)
      |                                             ^~~~~~~~~~~~~~~~~~~~~
./include/linux/pm.h:343:20: note: in definition of macro 'SET_RUNTIME_PM_OPS'
  343 |  .runtime_resume = resume_fn, \
      |                    ^~~~~~~~~

Fixes: 5ec55823 ("net: stmmac: add clocks management for gmac driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c

@@ -704,7 +704,6 @@ int stmmac_pltfr_remove(struct platform_device *pdev)
 }
 EXPORT_SYMBOL_GPL(stmmac_pltfr_remove);
 
-#ifdef CONFIG_PM_SLEEP
 /**
  * stmmac_pltfr_suspend
  * @dev: device pointer
@@ -712,7 +711,7 @@ EXPORT_SYMBOL_GPL(stmmac_pltfr_remove);
  * call the main suspend function and then, if required, on some platform, it
  * can call an exit helper.
  */
-static int stmmac_pltfr_suspend(struct device *dev)
+static int __maybe_unused stmmac_pltfr_suspend(struct device *dev)
 {
 	int ret;
 	struct net_device *ndev = dev_get_drvdata(dev);
@@ -733,7 +732,7 @@ static int stmmac_pltfr_suspend(struct device *dev)
  * the main resume function, on some platforms, it can call own init helper
  * if required.
  */
-static int stmmac_pltfr_resume(struct device *dev)
+static int __maybe_unused stmmac_pltfr_resume(struct device *dev)
 {
 	struct net_device *ndev = dev_get_drvdata(dev);
 	struct stmmac_priv *priv = netdev_priv(ndev);
@@ -745,7 +744,7 @@ static int stmmac_pltfr_resume(struct device *dev)
 	return stmmac_resume(dev);
 }
 
-static int stmmac_runtime_suspend(struct device *dev)
+static int __maybe_unused stmmac_runtime_suspend(struct device *dev)
 {
 	struct net_device *ndev = dev_get_drvdata(dev);
 	struct stmmac_priv *priv = netdev_priv(ndev);
@@ -755,14 +754,13 @@ static int stmmac_runtime_suspend(struct device *dev)
 	return 0;
 }
 
-static int stmmac_runtime_resume(struct device *dev)
+static int __maybe_unused stmmac_runtime_resume(struct device *dev)
 {
 	struct net_device *ndev = dev_get_drvdata(dev);
 	struct stmmac_priv *priv = netdev_priv(ndev);
 
 	return stmmac_bus_clks_config(priv, true);
 }
-#endif /* CONFIG_PM_SLEEP */
 
 const struct dev_pm_ops stmmac_pltfr_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(stmmac_pltfr_suspend, stmmac_pltfr_resume)