Ambari currently only supports upgrading the entire HDP stack together. Individual component upgrades are not supported.
However, we are planning "patch upgrades" (https://issues.apache.org/jira/browse/AMBARI-12556) which would allow you to upgrade only a single component of the stack. This is targeted for the Ambari 3.0 release.
Also it is not suggested to manually upgrade individually components of HDP. You should stick to the components which are shipped with the whole HDP stack. These are tested and certified together.