BACKPORT: dma-buf: heaps: Move heap-helper logic into the cma_heap implementation

Since the heap-helpers logic ended up not being as generic as
hoped, move the heap-helpers dma_buf_ops implementations into
the cma_heap directly.

This will allow us to remove the heap_helpers code in a following
patch.

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 a5d2d29e
git: //anongit.freedesktop.org/drm/drm-misc
tags/drm-misc-next-2020-11-27)
Link: https://lore.kernel.org/patchwork/patch/1343068/


Change-Id: I4672138353629a61c67ad7ad8aa03d7ebc6d98ed
Signed-off-by: John Stultz <john.stultz@linaro.org>
[hridya: patch needed minor rebase to accomodate the kernel allocation
interface]
Signed-off-by: Hridya Valsaraju <hridya@google.com>