Use modulo for WIZnet W5500 TCP over IP server socket connection acceptance index wrap around calculation

[apcountryman]

Resolves #2424 (Use modulo for WIZnet W5500 TCP over IP server socket connection acceptance index wrap around calculation).

This pull request:

• [ ] Implements a bug fix
• [ ] Implements an enhancement to an existing feature
• [ ] Implements a new feature
• [x] Performs a refactoring

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@apcountryman