add CFG_TUSB_OS_INC_PATH for os include path

useful for freertos/ prefix with esp IDF

examples/device/cdc_msc_freertos/Makefile

@@ -7,12 +7,18 @@ FREERTOS_SRC = lib/FreeRTOS-Kernel
 
 INC += \
 	src \
+	src/FreeRTOSConfig \
 	$(TOP)/hw \
 	$(TOP)/$(FREERTOS_SRC)/include \
 	$(TOP)/$(FREERTOS_SRC)/portable/GCC/$(FREERTOS_PORT)
 	
 # Example source
-EXAMPLE_SOURCE += $(wildcard src/*.c)
+EXAMPLE_SOURCE = \
+	src/freertos_hook.c \
+	src/main.c \
+	src/msc_disk.c \
+	src/usb_descriptors.c
+
 SRC_C += $(addprefix $(CURRENT_PATH)/, $(EXAMPLE_SOURCE))
 
 # FreeRTOS source, all files in port folder