MAX_BW divisor: N=0 and N=1 are unrestricted, N>=2 paces

In the internal transmitter-to-switch scheduler contract, a MAX_BW value of 0 or 1 means full rate, and N>=2 means at most one accepted transfer every N switch cycles. Pacing must be measured between valid_out && ready_in handshakes, not between send-state entries. Clamp the reload to 0 when the effective N is <=1, otherwise N=1 creates a spurious one-cycle gap.