tty: serdev: core: Fix misspelled function name __serdev_device_driver_register()

Fixes the following W=1 kernel build warning(s):

 drivers/tty/serdev/core.c:809: warning: expecting prototype for serdev_driver_register(). Prototype was for __serdev_device_driver_register() instead

Cc: Rob Herring <robh@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: linux-serial@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210520121906.3468725-3-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serdev/core.c

@@ -798,7 +798,7 @@ void serdev_controller_remove(struct serdev_controller *ctrl)
 EXPORT_SYMBOL_GPL(serdev_controller_remove);
 
 /**
- * serdev_driver_register() - Register client driver with serdev core
+ * __serdev_device_driver_register() - Register client driver with serdev core
  * @sdrv:	client driver to be associated with client-device.
  * @owner:	client driver owner to set.
  *