Android builds using linux-linaro should drop the Gator repo from their manifest

The linux-linaro kernel will contain the source code for the Gator module as this is one of the ARM LT's topic branches. This means that any Android build based on this kernel should drop the separate gator repo from its manifest file, otherwise their will be a build error.

I did this for vexpress [1] and if other boards, like Origen, start using linux-linaro for it's Android kernel then they need to do similar.