[adjustment] fix regression caused by commit b49541ced4
[adjustment] fix regression caused by commit b49541ced4

This patch restores the previous behaviour of mx_adjustment_interpolate.

Patch from Chris Lord <chris@linux.intel.com>

Fixes http://bugzilla.moblin.org/show_bug.cgi?id=7098

jonnylamb/mx,jonnylamb/mx,clutter-project/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx,pwithnall/mx,pwithnall/mx,clutter-project/mx,jonnylamb/mx,clutter-project/mx