e2tools: add .hash file
Fixes:
http://autobuild.buildroot.org/results/008/008df073bfa99f93e27d977ef1b64b79ef8b34c4/
http://autobuild.buildroot.org/results/28f/28f0e730768bfaf9577069e4ab18b5a3f3e595a8/
Similar to jquery-keyboard, it seems the e2tools tarball on the autobuilder
is corrupt. Fix it by adding a .hash file so it falls back to our s.b.o
mirror.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>