That's an odd notion...
There are actually very few "vehicle feats" in Star Wars, and practically none that would be of any use to someone riding a horse.
Some SW PrCs have a special ability like "Vehicle Familiarity" which gives a bonus to the piloting skill when using a specific vehicle... For example, Han Solo might have vehicle familiarity with the Millenium Falcon and gets a +2 bonus to pilot checks when flying it, but would lose that bonus when flying any other ship, even another YT-1300.
I suppose that could be applied to the ride check when riding a specific horse...
Most of the others are proficiency feats that counteract penalties when operating a class of starship.
Really, you'd be better off sticking with the D&D feats.