Even in the ocmem case, the allocated ocmem buffer size should match the
requested size.

v2: Move stray hunk to previous patch, make OCMEM size mismatch an error
    condition.
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/549759/