drm/amdgpu: export vm update mapping interface

It will be used by kfd to map svm range to GPU, because svm range does
not have amdgpu_bo and bo_va, cannot use amdgpu_bo_update interface, use
amdgpu vm update interface directly.

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>