amdgpu: add amdgpu_bo_va_op for va map/unmap support v3

The following interfaces are changed accordingly:
- amdgpu_bo_alloc
- amdgpu_create_bo_from_user_mem

v2: update the interfaces
v3: remove virtual_mc_base_address from amdgpu_bo

Signed-off-by: Jammy Zhou <Jammy.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>