If the deceleration is indeed constant, or linear, then it will take the same amount of time to go from 200 to 100 as it does to go from 100 to zero. The distance covered during the 200 to 100 deceleration will be three times the distance covered while decelerating from 100 to zero however.
However, in real life, air resistance is helping the brakes stop the car and at 200 mph, air resistance is four times as much as at 100 mph. For most cars, the air resistance at 200 mph is so extreme that you can slow down to 100 in a very short time just by closing the throttle, especially on a lightweight vehicle such as a motorcycle. So in real life, it will likely take less time to go from 200 to 100 than it takes to go from 100 to zero.
Birdshot from a shotgun comes out of the barrel at about 850 mph, it only takes forty yards of distance for the velocity to only be half that much, that’s how extreme air resistance is at high speed.
In addition, when you consider that most cars actually capable of 200 mph speeds, F-1 race cars and Indy cars, employ downforce from upside down wings for more traction at high speeds, in addition to the extreme air resistance at 200 mph, you also have downforce from the wing that’s over four times the weight of the car loading the tires, the deceleration from 200 to 100 is likely much quicker than the deceleration from 100 to zero.