media: ipu6: not override the dma_ops of device in driver

DMA ops are a helper for architectures and not for drivers to override the
DMA implementation. Driver should not override the DMA implementation.

This patch removes the dma_ops override from auxiliary device and adds
driver-internal helpers that use the actual DMA mapping APIs.

Fixes: 9163d835 ("media: intel/ipu6: add IPU6 DMA mapping API and MMU table")
Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[Sakari Ailus: Fix the commit message a little.]
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>