fix loading of bluetooth modules

mk/modules.mk

@@ -1312,6 +1312,7 @@ $(eval $(call KMOD_template,SND_USB_AUDIO,snd-usb-audio,\
 #
 
 $(eval $(call KMOD_template,BT,bt,\
+	$(MODULES_DIR)/kernel/net/ieee802154/6lowpan_iphc \
 	$(MODULES_DIR)/kernel/net/bluetooth/bluetooth \
 ,70))