dmaengine: mediatek: Add MediaTek Command-Queue DMA controller for MT6765 SoC

MediaTek Command-Queue DMA controller (CQDMA) on MT6765 SoC is dedicated
to memory-to-memory transfer through queue based descriptor management.

There are only 3 physical channels inside CQDMA, while the driver is
extended to support 32 virtual channels for multiple dma users to issue
dma requests onto the CQDMA simultaneously.

Signed-off-by: Shun-Chih Yu <shun-chih.yu@mediatek.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>