USB: add remove_id sysfs attr for usb drivers

Accroding commit 0994375e, which is adding remove_id sysfs attr
for pci drivers, for management tools dynamically bind/unbind
a pci/usb devices to a specified drivers; with this patch,
the management tools can be simplied.

And the original code didn't handle the failure of
usb_create_newid_file, fixed in this patch.

Signed-off-by: CHENG Renquan <rqcheng@smu.edu.sg>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index 7772928..deb6b48 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -144,3 +144,16 @@
 
 		Write a 1 to force the device to disconnect
 		(equivalent to unplugging a wired USB device).
+
+What:		/sys/bus/usb/drivers/.../remove_id
+Date:		November 2009
+Contact:	CHENG Renquan <rqcheng@smu.edu.sg>
+Description:
+		Writing a device ID to this file will remove an ID
+		that was dynamically added via the new_id sysfs entry.
+		The format for the device ID is:
+		idVendor idProduct.	After successfully
+		removing an ID, the driver will no longer support the
+		device.  This is useful to ensure auto probing won't
+		match the driver to the device.  For example:
+		# echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id