serdev: Introduce devm_serdev_device_open()

Add code implementing managed version of serdev_device_open() for
serdev device drivers that "open" the device during driver's lifecycle
only once (e.g. opened in .probe() and closed in .remove()).

Acked-by: Philippe Ombredanne <pombredanne@nexb.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
index c180045..7c1bb3d 100644
--- a/Documentation/driver-model/devres.txt
+++ b/Documentation/driver-model/devres.txt
@@ -384,6 +384,9 @@
   devm_reset_control_get()
   devm_reset_controller_register()
 
+SERDEV
+  devm_serdev_device_open()
+
 SLAVE DMA ENGINE
   devm_acpi_dma_controller_register()