drm/amdgpu: Implement intersect/compatible functions

Implemented a new intersect and compatible callback function
fetching start offset from backend drm buddy allocator.

Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220820073304.178444-3-Arunpravin.PaneerSelvam@amd.com