drm/pagemap: Use struct drm_pagemap_addr in mapping and copy functions

drm/pagemap: Use struct drm_pagemap_addr in mapping and copy functions

This struct embeds more information than just the DMA address. This will
help later to support folio orders greater than zero. At this point, there
is no functional change as the only struct member used is addr.

In Xe, adapt to the new drm_gpusvm_devmem_ops type signatures using struct
drm_pagemap_addr, as well as the internal xe SVM functions implementing
those operations. The use of this struct is propagated to xe_migrate as it
makes indexed accesses to the next DMA address but they are no longer
contiguous.

v2:
- Rename drm_pagemap_device_addr to drm_pagemap_addr (Matthew Brost)
- Squash with patch for Xe (Matthew Brost)
- Set proto and dir for completeness (Matthew Brost)
- Assess DMA map protocol (Matthew Brost)

Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://lore.kernel.org/r/20250805140028.599361-3-francois.dugast@intel.com
Signed-off-by: Francois Dugast <francois.dugast@intel.com>