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 <[e-mail]>
Signed-off-by: Francesco Dolcini <[e-mail]>
Reviewed-by: Linus Walleij <[e-mail]>
Reviewed-by: Marcel Ziswiler <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/mfd/stmpe.c

···
 
 	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")) {