phy: zynqmp: Fix unused-function compiler warning

Mark xpsgtr_suspend and xpsgtr_resume as __maybe_unused to fix the
following compiler warning when building with !CONFIG_PM_SLEEP:

drivers/phy/xilinx/phy-zynqmp.c:830:12: warning: ‘xpsgtr_resume’ defined but not used [-Wunused-function]
  830 | static int xpsgtr_resume(struct device *dev)
      |            ^~~~~~~~~~~~~
drivers/phy/xilinx/phy-zynqmp.c:819:12: warning: ‘xpsgtr_suspend’ defined but not used [-Wunused-function]
  819 | static int xpsgtr_suspend(struct device *dev)
      |            ^~~~~~~~~~~~~~

Also drop the existing #ifdef CONFIG_PM so the functions are always
compile-checked regardless of CONFIG_PM and/or CONFIG_PM_SLEEP being
set.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Link: https://lore.kernel.org/r/20200701141017.26931-1-tklauser@distanz.ch
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/xilinx/phy-zynqmp.c

@@ -815,8 +815,7 @@ static struct phy *xpsgtr_xlate(struct device *dev,
  * Power Management
  */
 
-#ifdef CONFIG_PM
-static int xpsgtr_suspend(struct device *dev)
+static int __maybe_unused xpsgtr_suspend(struct device *dev)
 {
 	struct xpsgtr_dev *gtr_dev = dev_get_drvdata(dev);
 
@@ -827,7 +826,7 @@ static int xpsgtr_suspend(struct device *dev)
 	return 0;
 }
 
-static int xpsgtr_resume(struct device *dev)
+static int __maybe_unused xpsgtr_resume(struct device *dev)
 {
 	struct xpsgtr_dev *gtr_dev = dev_get_drvdata(dev);
 	unsigned int icm_cfg0, icm_cfg1;
@@ -854,7 +853,6 @@ static int xpsgtr_resume(struct device *dev)
 
 	return 0;
 }
-#endif /* CONFIG_PM */
 
 static const struct dev_pm_ops xpsgtr_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(xpsgtr_suspend, xpsgtr_resume)