mfd: stmpe: Support disabling sub-functions

Add support of sub-functions disabling. It allows one to define
an stmpe sub-function device in devicetree, but keep it disabled.
Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211027082155.206449-1-francesco.dolcini@toradex.com

drivers/mfd/stmpe.c

@@ -1361,7 +1361,7 @@ static void stmpe_of_probe(struct stmpe_platform_data *pdata,
 
 	pdata->autosleep = (pdata->autosleep_timeout) ? true : false;
 
-	for_each_child_of_node(np, child) {
+	for_each_available_child_of_node(np, child) {
 		if (of_node_name_eq(child, "stmpe_gpio")) {
 			pdata->blocks |= STMPE_BLOCK_GPIO;
 		} else if (of_node_name_eq(child, "stmpe_keypad")) {