msm: kgsl: remove the iova partition from kgsl_layout

Since we manage our VA space differently, there's no need
to request a partition in our domains. This saves about 131kb
of gen_pool bitmap, per process, that was never used.

Change-Id: I963a6cbebeb9970d3fe643f7044083aa7b2038a1
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>