msm: kgsl: Remove warm/cold start

4xx was the only target that used "warm" start for bootstrap. Since that
is now gone we can remove the rest of the infrastructure and clean things
up a bit.

Change-Id: Ic0dedbad701559ae9a448c1a674cd0c1aea0fbab
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>