Remove vp10's build dependency on vp9

CONFIG_VP9_HIGHBITDEPTH is currently used by both vp9 and vp10, but in
many place outside vp9/vp10, the macro was used in conjunction of
CONFIG_VP9. This created a dependency on vp9 for vp10 to build. This
commit removes the dependency by use CONFIG_VP9_HIGHBITDEPTH only in
these places.

Change-Id: I8cc007fc9cf132394c6498ce6759e606b64a6ad0