Merge "clat: slightly increase MAXMTU and add comments" am: 9e9da0f3a5

Original change: https://android-review.googlesource.com/c/platform/external/android-clat/+/2393652

Change-Id: Ibf8d47a75e0c68c0078ae06d94e875a216c014ac
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>