Doc: ABI: testing: configfs-usb-gadget-sourcesink

commit 4bc58eb1 upstream.

Fix the name of attribute
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

Documentation/ABI/testing/configfs-usb-gadget-sourcesink

@@ -9,4 +9,4 @@ Description:
 		isoc_maxpacket	- 0 - 1023 (fs), 0 - 1024 (hs/ss)
 		isoc_mult	- 0..2 (hs/ss only)
 		isoc_maxburst	- 0..15 (ss only)
-		qlen		- buffer length
+		buflen		- buffer length