cm: Revert the new boot animation generation process

The servers do not have ImageMagick installed right now,
breaking the automated builds.

Revert this for now.

This reverts the following commits:
840e7814 bootanim: Use a for loop to make part# folders
ce5405d1 Fix wrong bootanimation.zip from mkdir .../part{0..2}
6179d949 cm: Build bootanimation.zip
67ddf372 cm: Rework boot animation generation

Change-Id: I63fc43da9b1a6afea5f791e879f0bfc9a385d98d