remove extra linker warning with old debug code
diff --git a/MakefileBasedBuild/app/conf_usb.h b/MakefileBasedBuild/app/conf_usb.h
index e11f5e1..0d7f81e 100644
--- a/MakefileBasedBuild/app/conf_usb.h
+++ b/MakefileBasedBuild/app/conf_usb.h
@@ -42,8 +42,5 @@
 #define ASSERT(x) do { if (!(x)) { dbgPrintf("%s:%d ASSERT failed: %s\n", __FILE__, __LINE__, #x); halt(); } } while (0)
 #define panic(fmt, ...) do{ dbgPrintf("panic at %s: " fmt, __func__, ##__VA_ARGS__); halt(); } while (0)
 
-#undef printf
-#define printf(x...) ERROR_DONT_USE_PRINTF
-
 #endif