net/bwping: Update to 2.1

[rhurlin]

Summary

From the changelog[1]

• Performance: added support for filtering incoming packets at the kernel level using BPF (if available on target platform)
• Various minor fixes and improvements.

[1] https://github.com/oleg-derevenetz/bwping/releases/tag/RELEASE_2.1

Tested on Poudriere. 'portlint -AC' is fine.

Submitted by Oleg Derevenetz <[e-mail]> (maintainer) in PR 250016

[arrowd]