ebtables: add hash file

Should clean up download failures like:
http://autobuild.buildroot.net/results/3c6/3c6b15a3d7ba84b7b3c257089569e2f615ec81b2/
http://autobuild.buildroot.net/results/4ee/4ee41e1616184687f56c9e3095885549ac4767d2/
http://autobuild.buildroot.net/results/9c6/9c623e3d9fde75b3dc1724909f6dc9738b12a207/



and more.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>