radeon: Use upload manager for buffer downloads
radeon: Use upload manager for buffer downloads

Using DMA for reads is much faster.

Signed-off-by: Niels Ole Salscheider <bc047973045f1d2e18db9e235943b01543fa2794@salscheider-online.de>
Signed-off by: Marek Olšák <marek.olsak@amd.com>

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