FROMLIST: drm/msm/a6xx: Use the DMA API for GMU memory objects

The GMU has very few memory allocations and uses a flat memory space so
there is no good reason to go out of our way to bypass the DMA APIs which
were basically designed for this exact scenario.

v2: Pass force_dma false to of_dma_configure to require that the DMA
region be set up and return error from of_dma_configure to fail probe.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Link: https://lore.kernel.org/lkml/1582223216-23459-5-git-send-email-jcrouse@codeaurora.org/
Change-Id: I4868cc684c5201d75e8bdba2bb4e2f949794f98d