crypto: Some minor cleanups to poly1305

- Use 'uint8_t' instead of 'unsigned char', being more consistent with
other crypto code (e.g., chacha20)
- Add two more macros: POLY1305_KEY_SIZE, POLY1305

crypto: Some minor cleanups to poly1305

- Use 'uint8_t' instead of 'unsigned char', being more consistent with
other crypto code (e.g., chacha20)
- Add two more macros: POLY1305_KEY_SIZE, POLY1305_MAC_SIZE

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crypto: Adjust poly1305 and hook to build

- Use all uppercase for macro constant (i.e., POLY1305_BLOCK_SIZE).
- Add 'inline' to two helper functions: U8TO32(), U32TO8()

crypto: Import Poly1305 implementation from OpenBSD

This hash algorithm is required to implement the Chacha20-Poly1305 AEAD
cipher as required by the in-kernel WireGuard VPN.