Add ALLOW_TRAINER_MULTI to enable Multi-trainer on targets with PXX2 internal module

Please note that this requires the S.PORT connection to the internal ISRM to be cut, as it would otherwise be pulled low by the ISRM (without using it otherwise).

radio/src/targets/horus/CMakeLists.txt

@@ -212,6 +212,8 @@ endif()
 if(INTERNAL_MODULE_PXX1)
   add_definitions(-DHARDWARE_INTERNAL_MODULE)
   add_definitions(-DINTERNAL_MODULE_PXX1)
+else()
+  option(ALLOW_TRAINER_MULTI "Allow multimodule to be use as trainer input" OFF)
 endif()
 
 if(INTERNAL_MODULE_PXX2)
@@ -229,6 +231,10 @@ if(INTERNAL_MODULE_MULTI)
   add_definitions(-DINTERNAL_MODULE_MULTI)
 endif()
 
+if(ALLOW_TRAINER_MULTI)
+  add_definitions(-DALLOW_TRAINER_MULTI)
+endif()
+
 if(DISK_CACHE)
   set(SRC ${SRC} disk_cache.cpp)
   add_definitions(-DDISK_CACHE)