[can] guarantee strict TX wire order

[wdfk-prog]

Summary

Add strict local TX wire ordering on top of PR #8.

The generic CAN framework now defaults to at most one hardware-pending TX request at a time. This prevents a later request from being preloaded into another controller mailbox and overtaking an earlier request because of controller-specific mailbox/identifier priority.

Drivers that can prove ordered transmission with multiple hardware mailboxes may opt into:

RT_CAN_CAP_TX_ORDERED_MAILBOX

and retain multi-mailbox preload.

Ordering contract

For the generic fallback:

• framework admission order is FIFO;
• only the queue head may be submitted;
• a later request cannot bypass queued work;
• a failed/busy submit never uses force-overwrite or tail reinsertion;
• without RT_CAN_CAP_TX_ORDERED_MAILBOX, the next request is submitted only after the previous hardware-owned request reaches a terminal event.

This addresses the class of ordering problems discussed in RT-Thread issue/PR RT-Thread#11270 while keeping the hardware capability explicit.

Compatibility

The capability is queried through control(RT_CAN_CMD_GET_CAPABILITIES, ...). Existing BSPs that do not implement the command naturally fall back to strict single-pending ordering and require no ISR call-site changes.

Tests

The fake-controller test exposes three mailboxes and submits CAN IDs in the order 0x700 -> 0x100 -> 0x300. With no ordered-mailbox capability, the test verifies that only one request is submitted to hardware at a time and the same application order is preserved across TX_DONE events.

No target-board/hardware validation has been performed in this PR.

Stack

PR 4/7. Base: PR #8 (refactor/can-tx-terminal-timeout).

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