Add a new operation to replace mappings in a VM with a new one.

v2: Fix Jerry's comment, separate out clear operation.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NJunwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>