Constant rubble::link::MIN_PDU_BUF

pub const MIN_PDU_BUF: usize = MIN_PAYLOAD_BUF + 2; // 0x0000_0000_0000_0027usize

Min. size a Link-Layer PDU buffer must have (to cover both advertising and data channels).

Bluetooth 4.2 also allows exchanging larger PDUs using the Packet Length Extension, but Rubble does not currently support that.