Update:
I found that I was missing can.ko and can-raw.ko from net/can. I already got slcan from drivers/net/can
When adding these to the application image then the network is stopped by a kernel bug/panic. This kernel bug is reported for net/netlink/af_netlink.c:1315. The modules are still being compiled and runned on 2.13.1+rev1.dev resinOS image
Note: Target is unaccesable after kernel bug/panic. A re-installation is needed
From my understanding then CAN supported can only be available if can.ko (CONFIG_CAN) raw and can-raw.ko (CONFIG_CAN_RAW) are provided by the kernel and not being loaded by via kernel modules. Then it is up to resin users to compile what ever CAN driver they need. I my case slcan.
Anyone got an idea?