Input: zinitix - don't fail if linux,keycodes prop is absent

When initially adding the touchkey support, a mistake was made in the
property parsing code. The possible negative errno from
device_property_count_u32() was never checked, which was an oversight
left from converting to it from the of_property as part of the review
fixes.

Re-add the correct handling of the absent property, in which case zero
touchkeys should be assumed, which would disable the feature.

Reported-by: Jakob Hauser <[e-mail]>
Tested-by: Jakob Hauser <[e-mail]>
Fixes: 075d9b22c8fe ("Input: zinitix - add touchkey support")
Reviewed-by: Linus Walleij <[e-mail]>
Signed-off-by: Nikita Travkin <[e-mail]>
Tested-by: Yassine Oudjana <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/touchscreen/zinitix.c

···
 		return error;
 	}
 
-	bt541->num_keycodes = device_property_count_u32(&client->dev, "linux,keycodes");
-	if (bt541->num_keycodes > ARRAY_SIZE(bt541->keycodes)) {
-		dev_err(&client->dev, "too many keys defined (%d)\n", bt541->num_keycodes);
-		return -EINVAL;
-	}
+	if (device_property_present(&client->dev, "linux,keycodes")) {
+		bt541->num_keycodes = device_property_count_u32(&client->dev,
+								"linux,keycodes");
+		if (bt541->num_keycodes < 0) {
+			dev_err(&client->dev, "Failed to count keys (%d)\n",
+				bt541->num_keycodes);
+			return bt541->num_keycodes;
+		} else if (bt541->num_keycodes > ARRAY_SIZE(bt541->keycodes)) {
+			dev_err(&client->dev, "Too many keys defined (%d)\n",
+				bt541->num_keycodes);
+			return -EINVAL;
+		}
 
-	error = device_property_read_u32_array(&client->dev, "linux,keycodes",
-					       bt541->keycodes,
-					       bt541->num_keycodes);
-	if (error) {
-		dev_err(&client->dev,
-			"Unable to parse \"linux,keycodes\" property: %d\n", error);
-		return error;
+		error = device_property_read_u32_array(&client->dev,
+						       "linux,keycodes",
+						       bt541->keycodes,
+						       bt541->num_keycodes);
+		if (error) {
+			dev_err(&client->dev,
+				"Unable to parse \"linux,keycodes\" property: %d\n",
+				error);
+			return error;
+		}
 	}
 
 	error = zinitix_init_input_dev(bt541);