Input: gpio-keys - add support for linux,input-value DTS property

Allows setting the value of EV_ABS events from DTS.
This property is included in the gpio-keys.yaml scheme, but was only
implemented for gpio-keys-polled.

Signed-off-by: Gergo Koteles <soyer@irl.hu>
Link: https://lore.kernel.org/r/3519a11b0ef5324a2befbd137cd2aa0cb8fd057d.1676850819.git.soyer@irl.hu
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/keyboard/gpio_keys.c

@@ -770,6 +770,9 @@ gpio_keys_get_devtree_pdata(struct device *dev)
 					     &button->type))
 			button->type = EV_KEY;
 
+		fwnode_property_read_u32(child, "linux,input-value",
+					 (u32 *)&button->value);
+
 		button->wakeup =
 			fwnode_property_read_bool(child, "wakeup-source") ||
 			/* legacy name */