recipes: Update cmake-mode recipe.

`cmake-mode.el' is now hosted in the cmake git and it comes with
autoloads and everything.

./test-recipe.sh output: *** SUCCESS ../recipes/cmake-mode.rcp ***

Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
Merge pull request #1657 from ruediger/cmake-mode-update

recipes: Update cmake-mode recipe.