USB: update documentation for URB_ISO_ASAP

This patch (as1611) updates the USB documentation and kerneldoc to
give a more precise meaning for the URB_ISO_ASAP flag and to explain
more of the details of scheduling for isochronous URBs.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/usb/error-codes.txt b/Documentation/usb/error-codes.txt
index b3f606b..8d1e2a9 100644
--- a/Documentation/usb/error-codes.txt
+++ b/Documentation/usb/error-codes.txt
@@ -35,9 +35,8 @@
 		d) ISO: number_of_packets is < 0
 		e) various other cases
 
--EAGAIN		a) specified ISO start frame too early
-		b) (using ISO-ASAP) too much scheduled for the future
-		   wait some time and try again.
+-EXDEV		ISO: URB_ISO_ASAP wasn't specified and all the frames
+		the URB would be scheduled in have already expired.
 
 -EFBIG		Host controller driver can't schedule that many ISO frames.