drm/amdgpu: move get_user_pages out of amdgpu_ttm_tt_pin_userptr v6
That avoids lock inversion between the BO reservation lock
and the anon_vma lock.
v2:
* Changed amdgpu_bo_list_entry.user_pages to an array of pointers
* Lock mmap_sem only for get_user_pages
* Added invalidation of unbound userpointer BOs
* Fixed memory leak and page reference leak
v3 (chk):
* Revert locking mmap_sem only for_get user_pages
* Revert adding invalidation of unbound userpointer BOs
* Sanitize and fix error handling
v6 (chk):
* Fix error handling when we run out of tries.
Signed-off-by: Christian König <christian.koenig@amd.com> Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com> Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com> (v4) Acked-by: Alex Deucher <alexander.deucher@amd.com>