Restrict ref mv search range.
Experiment to test speed trade off of reducing the extent of the ref mv search. Reducing the maximum number of tested candidates to 9 had minimal net effect on quality in any of the tests sets. Reduction to 7 has a small negative impact (worst was STD-HD at about -0.2%). This change is in response to the apparently high number of decode cycles reported in regard to mv-ref selection. Change-Id: I0e92e92e324337689358495a1ec9ccdeb23dc774