MIPS: alchemy: Fix build breakage, if TOUCHSCREEN_WM97XX is disabled

Only include wm97xx touchscreen probing code, if driver is enabled.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/alchemy/devboards/db1300.c

@@ -731,6 +731,7 @@ static struct platform_device db1300_lcd_dev = {
 
 /**********************************************************************/
 
+#if IS_ENABLED(CONFIG_TOUCHSCREEN_WM97XX)
 static void db1300_wm97xx_irqen(struct wm97xx *wm, int enable)
 {
 	if (enable)
@@ -762,6 +763,12 @@ static int db1300_wm97xx_probe(struct platform_device *pdev)
 
 	return wm97xx_register_mach_ops(wm, &db1300_wm97xx_ops);
 }
+#else
+static int db1300_wm97xx_probe(struct platform_device *pdev)
+{
+	return -ENODEV;
+}
+#endif
 
 static struct platform_driver db1300_wm97xx_driver = {
 	.driver.name	= "wm97xx-touch",