gpio: mockup: Fix mode of debugfs files

This driver's debugfs files have had a read operation since commit
2a9e2740 ("gpio: mockup: rework debugfs interface"), but were
still being created with write-only mode bits.  Update them to
indicate that the files can also be read.
Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Fixes: 2a9e2740 ("gpio: mockup: rework debugfs interface")
Cc: stable@kernel.org # v5.1+
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/gpio-mockup.c

@@ -369,7 +369,7 @@ static void gpio_mockup_debugfs_setup(struct device *dev,
 		priv->offset = i;
 		priv->desc = gpiochip_get_desc(gc, i);
 
-		debugfs_create_file(name, 0200, chip->dbg_dir, priv,
+		debugfs_create_file(name, 0600, chip->dbg_dir, priv,
 				    &gpio_mockup_debugfs_ops);
 	}
 }