Remove enum types which are duplicated and cause error on webkit style checker.

DistanceModel and PanningModel emuns are duplicated with distance and panner.
It doesn't need to be declared in pannerNode.

BUG=none

Review URL: https://codereview.chromium.org/246783003

git-svn-id: svn://svn.chromium.org/blink/trunk@172167 bbb929c8-8fbe-4397-9dbb-9b2b20218538