drivers: change struct device_driver::coredump() return type to void

Upon submitting a patch for mwifiex [1] it was discussed whether this
callback function could fail. To keep things simple there is no need
for the error code so the driver can do the task synchronous or not
without worries. Currently the device driver core already ignores the
return value so changing it to void.

[1] https://patchwork.kernel.org/patch/10231933/Signed-off-by: Arend van Spriel <aspriel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/device.h

@@ -256,7 +256,9 @@ enum probe_type {
  *		automatically.
  * @pm:		Power management operations of the device which matched
  *		this driver.
- * @coredump:	Called through sysfs to initiate a device coredump.
+ * @coredump:	Called when sysfs entry is written to. The device driver
+ *		is expected to call the dev_coredump API resulting in a
+ *		uevent.
  * @p:		Driver core's private data, no one other than the driver
  *		core can touch this.
  *
@@ -288,7 +290,7 @@ struct device_driver {
 	const struct attribute_group **groups;
 
 	const struct dev_pm_ops *pm;
-	int (*coredump) (struct device *dev);
+	void (*coredump) (struct device *dev);
 
 	struct driver_private *p;
 };