PM: Clear -EAGAIN in dpm_prepare

When the last device in the dpm list is unregistered directly after its
prepare() callback returned with -EAGAIN, the return code is passed to
the calling function, resulting in a suspend failure. Prevent this by
clearing the return code after -EAGAIN.
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

drivers/base/power/main.c

@@ -762,6 +762,7 @@ static int dpm_prepare(pm_message_t state)
 			dev->power.status = DPM_ON;
 			if (error == -EAGAIN) {
 				put_device(dev);
+				error = 0;
 				continue;
 			}
 			printk(KERN_ERR "PM: Failed to prepare device %s "