[usb]update usb stack

components/drivers/usb/SConscript

@@ -2,13 +2,12 @@
 import os
 from building import *
 
-cwd  = GetCurrentDir()
-objs = []
-list = os.listdir(cwd)
+cwd     = GetCurrentDir()
+objs 	= []
+list 	= os.listdir(cwd)
 
 for d in list:
     path = os.path.join(cwd, d)
     if os.path.isfile(os.path.join(path, 'SConscript')):
         objs = objs + SConscript(os.path.join(d, 'SConscript'))
-
 Return('objs')