msm: kgsl: Remove obsolete pre-production targets

We do not need to carry support for old pre-production GPU spins from
older kernels as we expect only the production version of that GPU
to be in active use from this point on.

Change-Id: Ic0dedbad1de068efedb5d76d271ea489d81b95f3
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>