oops - won't build with USB disabled

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1037 42af7a65-404d-4744-a932-0658087f49c3

arch/arm/src/common/up_internal.h

@@ -200,6 +200,7 @@ extern void up_netinitialize(void);
 extern void up_usbinitialize(void);
 extern void up_usbuninitialize(void);
 #else
+# define up_usbinitialize()
 # define up_netinitialize()
 #endif