fix end check in eagle

[jjjjohnson]

Motivation

After eagel2 target model verify, the accepted tokens might be EOS token, need to check each appended new token. Then free kv cache.

Modifications

Checklist

• Format your code according to the Contributor Guide.
• Add unit tests as outlined in the Contributor Guide.
• Update documentation as needed, including docstrings or example tutorials.

[merrymercy]

@yukavio can you help review this?