msm: kgsl: Don't allocate GMU dump memory if not used

Older targets used this scratch memory for debug purposes.
Newer targets don't use this memory so don't allocate it.

Change-Id: I4bfae0fc10eedb289c6765a15d95045f46ffb96e
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>