i2c: core: Use fwnode_for_each_child_node_scoped()

Replace the manual __free(fwnode_handle) iterator declaration with the
new scoped iterator macro for cleaner, less error-prone code.

This eliminates the need for explicit iterator variable declaration with
the cleanup attribute, making the code more consistent with other scoped
iterator usage patterns in the kernel.

Signed-off-by: Jean-François Lessard <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Reviewed-by: Sakari Ailus <[e-mail]>
Signed-off-by: Wolfram Sang <[e-mail]>

drivers/i2c/i2c-core-slave.c

···
 	struct fwnode_handle *fwnode = dev_fwnode(dev);
 
 	if (is_of_node(fwnode)) {
-		struct fwnode_handle *child __free(fwnode_handle) = NULL;
 		u32 reg;
 
-		fwnode_for_each_child_node(fwnode, child) {
+		fwnode_for_each_child_node_scoped(fwnode, child) {
 			fwnode_property_read_u32(child, "reg", &reg);
 			if (reg & I2C_OWN_SLAVE_ADDRESS)
 				return true;