USB: update documentation for usbmon

The documentation for usbmon is out of date; the usbfs "devices" file
now exists in /sys/kernel/debug/usb rather than /proc/bus/usb.  This
patch (as1505) updates the documentation accordingly, and also
mentions that the necessary information can be found by running lsusb.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Pete Zaitcev <zaitcev@redhat.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/usb/usbmon.txt

@@ -47,10 +47,11 @@ This allows to filter away annoying devices that talk continuously.
 
 2. Find which bus connects to the desired device
 
-Run "cat /proc/bus/usb/devices", and find the T-line which corresponds to
-the device. Usually you do it by looking for the vendor string. If you have
-many similar devices, unplug one and compare two /proc/bus/usb/devices outputs.
-The T-line will have a bus number. Example:
+Run "cat /sys/kernel/debug/usb/devices", and find the T-line which corresponds
+to the device. Usually you do it by looking for the vendor string. If you have
+many similar devices, unplug one and compare the two
+/sys/kernel/debug/usb/devices outputs. The T-line will have a bus number.
+Example:
 
 T:  Bus=03 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=12  MxCh= 0
 D:  Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
@@ -58,7 +59,10 @@ P:  Vendor=0557 ProdID=2004 Rev= 1.00
 S:  Manufacturer=ATEN
 S:  Product=UC100KM V2.00
 
-Bus=03 means it's bus 3.
+"Bus=03" means it's bus 3. Alternatively, you can look at the output from
+"lsusb" and get the bus number from the appropriate line. Example:
+
+Bus 003 Device 002: ID 0557:2004 ATEN UC100KM V2.00
 
 3. Start 'cat'