Fixes a mismatch introduced in a previous patch

Fixes a mismatch introdcuded with ext-inter + motion-var in
https://aomedia.googlesource.com/aom/+/42d9610a797dbc778797c04445578eba514d4099

Change-Id: I9d357b6db8fdbfccc7d95aaa196d5d0574ef431b
1 file changed