master: remove linux kernel git repo, no longer required

Kernels are now built from tarballs, cloning the SDK should be much
faster now! :)

Change-Id: Ic6ce8910760ddbdd95637a3e70bc79385d0b82c5
Merge pull request #54 from marineam/kernel

master: remove linux kernel git repo, no longer required
add(build-528): Add manifest for v528.0.0

Change-Id: I14dc516ea1b89b9f009b39496613537d8083d10a