spi: tegra20-slink: Declare runtime suspend and resume functions conditionally

The following build error is seen with CONFIG_PM=n.

drivers/spi/spi-tegra20-slink.c:1188:12: error:
	'tegra_slink_runtime_suspend' defined but not used
drivers/spi/spi-tegra20-slink.c:1200:12: error:
	'tegra_slink_runtime_resume' defined but not used

Declare the functions only if PM is enabled. While at it, remove the
unnecessary forward declarations.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20210907045358.2138282-1-linux@roeck-us.netSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-tegra20-slink.c

@@ -204,9 +204,6 @@ struct tegra_slink_data {
 	struct dma_async_tx_descriptor		*tx_dma_desc;
 };
 
-static int tegra_slink_runtime_suspend(struct device *dev);
-static int tegra_slink_runtime_resume(struct device *dev);
-
 static inline u32 tegra_slink_readl(struct tegra_slink_data *tspi,
 		unsigned long reg)
 {
@@ -1185,6 +1182,7 @@ static int tegra_slink_resume(struct device *dev)
 }
 #endif
 
+#ifdef CONFIG_PM
 static int tegra_slink_runtime_suspend(struct device *dev)
 {
 	struct spi_master *master = dev_get_drvdata(dev);
@@ -1210,6 +1208,7 @@ static int tegra_slink_runtime_resume(struct device *dev)
 	}
 	return 0;
 }
+#endif /* CONFIG_PM */
 
 static const struct dev_pm_ops slink_pm_ops = {
 	SET_RUNTIME_PM_OPS(tegra_slink_runtime_suspend,