USB: Documentation/usb/gadget_serial.txt: update to match driver use_acm behaviour

Commit 7bb5ea54 (usb gadget serial: use composite gadget framework)
changed the default for the use_acm parameter from 0 to 1.
Update the documentation to match.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/usb/gadget_serial.txt

@@ -114,11 +114,11 @@ modules.
 Then you must load the gadget serial driver.  To load it as an
 ACM device (recommended for interoperability), do this:
 
-  modprobe g_serial use_acm=1
+  modprobe g_serial
 
 To load it as a vendor specific bulk in/out device, do this:
 
-  modprobe g_serial
+  modprobe g_serial use_acm=0
 
 This will also automatically load the underlying gadget peripheral
 controller driver.  This must be done each time you reboot the gadget