For the 4.8 series instead:
4.8.0-rc8-powerpc #1 Debian 4.8~rc8-1~exp1 (2016-09-26)
4.8.0-1 Debian 4.8.5 -> broken
Since I saw no other 4.7 series, I can see that the breakage happened
already in the 4.8 series:, somewhere between:
linux-image-4.8.0-rc8-powerpc_4.8~rc8-1~exp1_powerpc.deb : 2016-09-29
04:29:33
linux-image-4.8.0-1-powerpc_4.8.5-1_powerpc.deb : 2016-11-02 03:31:50
I couldn't find any intermediate version to test (or later series of
the 4.7.x) , if there is one, please tell me. Does this however gives
you already a clue?