Set nunmber of UAVCAN interfaces on HW from top level cmake file

cmake/configs/nuttx_px4fmu-v2_default.cmake

@@ -2,6 +2,8 @@ include(nuttx/px4_impl_nuttx)
 
 set(CMAKE_TOOLCHAIN_FILE ${CMAKE_SOURCE_DIR}/cmake/toolchains/Toolchain-arm-none-eabi.cmake)
 
+set(config_uavcan_num_ifaces 2)
+
 set(config_module_list
 	#
 	# Board support modules

cmake/configs/nuttx_px4fmu-v4_default.cmake

@@ -2,6 +2,8 @@ include(nuttx/px4_impl_nuttx)
 
 set(CMAKE_TOOLCHAIN_FILE ${CMAKE_SOURCE_DIR}/cmake/toolchains/Toolchain-arm-none-eabi.cmake)
 
+set(config_uavcan_num_ifaces 1)
+
 set(config_module_list
 	#
 	# Board support modules

src/modules/uavcan/CMakeLists.txt

@@ -41,7 +41,7 @@ add_definitions(
 		-DUAVCAN_NO_ASSERTIONS
 		-DUAVCAN_PLATFORM=stm32
 		-DUAVCAN_STM32_${OS_UPPER}=1
-		-DUAVCAN_STM32_NUM_IFACES=2
+		-DUAVCAN_STM32_NUM_IFACES=${config_uavcan_num_ifaces}
 		-DUAVCAN_STM32_TIMER_NUMBER=5
 		)