spi: fsl-lpspi: Fix build warning when !CONFIG_PM

Add #ifdef CONFIG_PM guard to fix build warning when !CONFIG_PM
drivers/spi/spi-fsl-lpspi.c:810:12: warning: ‘fsl_lpspi_runtime_suspend’ defined but not used [-Wunused-function]
 static int fsl_lpspi_runtime_suspend(struct device *dev)
            ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/spi/spi-fsl-lpspi.c:789:12: warning: ‘fsl_lpspi_runtime_resume’ defined but not used [-Wunused-function]
 static int fsl_lpspi_runtime_resume(struct device *dev)
            ^~~~~~~~~~~~~~~~~~~~~~~~

Fixes: 944c01a889 ("spi: lpspi: enable runtime pm for lpspi")
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-lpspi.c

@@ -786,6 +786,7 @@ static irqreturn_t fsl_lpspi_isr(int irq, void *dev_id)
 	return IRQ_NONE;
 }
 
+#ifdef CONFIG_PM
 static int fsl_lpspi_runtime_resume(struct device *dev)
 {
 	struct spi_controller *controller = dev_get_drvdata(dev);
@@ -819,6 +820,7 @@ static int fsl_lpspi_runtime_suspend(struct device *dev)
 
 	return 0;
 }
+#endif
 
 static int fsl_lpspi_init_rpm(struct fsl_lpspi_data *fsl_lpspi)
 {