Increase ReadFdToString buffer size am: afb166083c

Original change: https://android-review.googlesource.com/c/platform/system/libbase/+/2380578

Change-Id: I03bbeb42aa54afaa0553e042072030394763d73a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>