tinyxml2: add .hash file
Fixes:
http://autobuild.buildroot.org/results/ae6/ae648f40e0f51628000b2d2297759c5fdf1b4d16/
http://autobuild.buildroot.org/results/799/79923f099bf0f2e88ccbb7fc2d3d92a85c167057/
Similar to jquery-keyboard, it seems the tinyxml2 tarball on the autobuilder
is corrupt. Fix it by adding a .hash file so it falls back to out s.b.o mirror.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>