usbcore: fix incorrect type in assignment in descriptors_changed()

This patch fixes the incorrect assignment of a variable with type 'le16'
to a variable with type 'unsigned int'.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>