gs101: set readahead_size_kb=128 to vendor, product and system_ext am: 2b741a51c5 am: a880d188d2

Original change: https://googleplex-android-review.googlesource.com/c/device/google/gs101/+/16549415

Change-Id: I28dea8e69ed3a66d1ac9575e2967e706e398f18d