avrdude: update to 8.1

[trustbyte]

Description

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 26.1 25B78 arm64
Command Line Tools 26.1.0.0.1.1761104275

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?