Raspberry Pi port, piCore-15.0 is available!
# uname -aLinux box 4.9.22-piCore-v7 #1 SMP Sat Apr 15 12:27:07 UTC 2017 armv7l GNU/Linux
$ tce-load -i -w net-usb-4.9.22-piCore-v7
net-bridging-4.9.22-piCore-v7 and net-sched-4.9.22-piCore-v7 posted
$ modinfo stpfilename: /lib/modules/4.9.22-piCore-v7/kernel.tclocal/net/802/stp.kosrcversion: AFBB842A0563D27C8F56BBFdepends: llcintree: Yvermagic: 4.9.22-piCore-v7 SMP mod_unload modversions ARMv7 p2v8
Perhaps you could test this out and, if things work, llc.ko could added to one of the extensions.