Update CVE-2017-13305/linux

It turned out that it is not Android specific, but rather an issue in
the keys subsystem and fixed upstream in 4.12-rc5 with upstream commit
794b4bc292f5d31739d89c0202c54e7dc9bc3add .

The fix was as well backported to 4.9-upstream-stable for 4.9.81 and
thus included in 4.9.82-1+deb9u1.

Thanks: nsl (Nicholas)