Move FreeRTOS model data to separate folder

Move model data used by the FreeRTOS application to separate folder to
allow for changing model easier by chaning the compile definition set in
CMakeLists.txt just after ethosu_add_executable_test(...)

Change-Id: I81d801c52e721f8ca7ad83892f9b68e82aee8188
diff --git a/applications/freertos/CMakeLists.txt b/applications/freertos/CMakeLists.txt
index 74cbe45..292f598 100644
--- a/applications/freertos/CMakeLists.txt
+++ b/applications/freertos/CMakeLists.txt
@@ -25,6 +25,7 @@
 ethosu_add_executable_test(freertos PRIVATE
     SOURCES main.cpp
     LIBRARIES freertos_kernel)
+target_include_directories(freertos PRIVATE models/mobilenet_v2)
 
 # Use the fast memory to support both 11.12.57 and 11.13.x release
 # of the FVP