rt2x00: Ignore set_state(STATE_SLEEP) failure

Some hardware never seem to accept the "goto sleep" command, since the legacy
drivers don't have suspend and resume handlers the entire code for it was
basically a educated guess (based on the "enable radio" code).
This patch will only print a warning when the "goto sleep" command fails, and
just continues as usual. Perhaps that means the device will not reach a sleep
state and consumes more power then it should, but it is equally possible it
simply needs some seconds longer to sleep. Anyway, by making the command
non-fatal it will not block the rest of the suspend procedure.
Signed-off-by: NIvo van Doorn <IvDoorn@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00dev.c

@@ -1393,11 +1393,20 @@ int rt2x00lib_suspend(struct rt2x00_dev *rt2x00dev, pm_message_t state)
 
 exit:
 	/*
-	 * Set device mode to sleep for power management.
+	 * Set device mode to sleep for power management,
+	 * on some hardware this call seems to consistently fail.
+	 * From the specifications it is hard to tell why it fails,
+	 * and if this is a "bad thing".
+	 * Overall it is safe to just ignore the failure and
+	 * continue suspending. The only downside is that the
+	 * device will not be in optimal power save mode, but with
+	 * the radio and the other components already disabled the
+	 * device is as good as disabled.
 	 */
 	retval = rt2x00dev->ops->lib->set_device_state(rt2x00dev, STATE_SLEEP);
 	if (retval)
-		return retval;
+		WARNING(rt2x00dev, "Device failed to enter sleep state, "
+			"continue suspending.\n");
 
 	return 0;
 }