dmaengine: qcom: simplify getting .drvdata

We should get drvdata from struct device directly. Going via
platform_device is an unneeded step back and forth.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>