Revert "PX4: enabled support for UAVCAN"

This reverts commit 71b2306a.

This broke the build due to git submodules. We need to work out how
ArduPilot is going to handle the external uavcan module dependency
before we enable this again

mk/PX4/ROMFS/init.d/rc.APM

@@ -345,13 +345,6 @@ else
     sh /etc/init.d/rc.error           
 fi
 
-if uavcan start 1
-then
-    echo "started uavcan OK"
-else
-    echo "failed to start uavcan"
-fi
-
 if mtd readtest /fs/mtd
 then
     echo "mtd readtest OK"

mk/PX4/config_px4fmu-v2_APM.mk

@@ -74,10 +74,6 @@ MODULES         += modules/libtomcrypt
 endif
 MODULES		+= lib/conversion
 
-MODULES		+= modules/uavcan
-MODULES		+= lib/mathlib
-LIBRARIES	+= lib/mathlib/CMSIS
-
 #
 # Transitional support - add commands from the NuttX export archive.
 #

mk/px4_targets.mk

@@ -31,7 +31,6 @@ PX4_GIT_VERSION   := $(shell cd $(PX4_ROOT) && git rev-parse HEAD | cut -c1-8)
 
 EXTRAFLAGS += -DNUTTX_GIT_VERSION="\"$(NUTTX_GIT_VERSION)\""
 EXTRAFLAGS += -DPX4_GIT_VERSION="\"$(PX4_GIT_VERSION)\""
-EXTRAFLAGS += -DUAVCAN=1
 
 # we have different config files for V1 and V2
 PX4_V1_CONFIG_FILE=$(MK_DIR)/PX4/config_px4fmu-v1_APM.mk