Hold tile control until datapath completion

[guosran]

Summary

Addresses #292 with a minimized tile control-completion fix. This PR only updates TileRTL.py.

Changes

• Keep FU control valid until both the FU and FU crossbar have completed.
• Let crossbars observe same-cycle FU completion.
• Avoid advancing tile control before all datapath consumers finish.

Validation

Part of the master-based small conv passing set.

[guosran]

Tile control should not advance just because the FU element is done if the FU crossbar still has to consume the output.

cycle N:
element_done = 1
fu_crossbar_done = 0

Before:
ctrl could advance and the FU output could be dropped.

After:
TileRTL keeps the current control active until the relevant datapath/crossbar completion is observed.