Rename Dhcp6Packet.decodePacket to Dhcp6Packet.decode. am: 24f0869490

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/2682768

Change-Id: I3a9f60f0761021381f1f4169132808318aacf3eb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>