BACKPORT: dma-buf: system_heap: Allocate higher order pages if available

While the system heap can return non-contiguous pages,
try to allocate larger order pages if possible.

This will allow slight performance gains and make implementing
page pooling easier.

Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Liam Mark <lmark@codeaurora.org>
Cc: Laura Abbott <labbott@kernel.org>
Cc: Brian Starkey <Brian.Starkey@arm.com>
Cc: Hridya Valsaraju <hridya@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sandeep Patil <sspatil@google.com>
Cc: Daniel Mentz <danielmentz@google.com>
Cc: Chris Goldsworthy <cgoldswo@codeaurora.org>
Cc: Ørjan Eide <orjan.eide@arm.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Ezequiel Garcia <ezequiel@collabora.com>
Cc: Simon Ser <contact@emersion.fr>
Cc: James Jones <jajones@nvidia.com>
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

Bug: 173440990
(cherry picked from commit d963ab0f
git: //anongit.freedesktop.org/drm/drm-misc
tags/drm-misc-next-2020-11-27)
Link: https://lore.kernel.org/patchwork/patch/1343070/


Change-Id: Ic30327f6163d2ba727d08bd2dfdcfcff858064dc
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Hridya Valsaraju <hridya@google.com>