Add support for use of a USB serial device to provide NSH console I/O. Verified on the Sure PIPIC32MX board

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4458 42af7a65-404d-4744-a932-0658087f49c3

nshlib/nsh_consolemain.c

@@ -105,7 +105,8 @@ int nsh_consolemain(int argc, char *argv[])
    */
 
 #ifdef HAVE_USB_CONSOLE
-  DEBUGASSERT(nsh_usbconsole() == OK);
+  ret = nsh_usbconsole();
+  DEBUGASSERT(ret == OK);
 #endif
 
   /* Present a greeting */