Claude review: drm/scdc-helper: Add scdc_status debugfs entry

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

This is the core patch and has a few issues:

**Bug: Off-by-one in SCDC read misses register 0xFF.**

```c
ret = drm_scdc_read(ddc, 0, buf, 128);
if (ret)
    return ret;

ret = drm_scdc_read(ddc, 127, &buf[127], 128);
```

The first read covers registers `0x00–0x7F`. The second reads from offset 127 (`0x7F`) for 128 bytes, covering `0x7F–0xFE`. Register `0xFF` is never read, and byte 127 is read twice (second overwrites first). The doc comment says "Reads the entire 256 byte SCDC state" but it only reads 255 registers. The hex dump then prints all 256 bytes including the unread byte 255 (which will be stale or zero).

The fix should be:
```c
ret = drm_scdc_read(ddc, 128, &buf[128], 128);
```

**Issue: `drm_connector_put()` placed mid-function on success path.**

```c
scdc_print_flag(m, "Low Rate Scrambling Supported", scdc->scrambling.low_rates);

drm_connector_put(connector);  // <-- refcount dropped here

scdc_print_flag(m, "Scrambling Enabled", st->scrambling_enabled);
// ... 10 more lines accessing st-> ...

return 0;

err_conn_put:
    drm_connector_put(connector);
    return ret;
```

The refcount is technically balanced (one get, one put per path), and the code after the put only accesses `st` (which lives in `priv`, not the connector), so it's memory-safe. But dropping the connector ref before the function completes is an unusual pattern. If future changes access `connector` or `scdc` below this point, they'd hit a use-after-potential-free. Consider moving the `put` to just before `return 0`, or restructuring with a single exit path.

**Minor: Typo in kdoc.**

```c
/** @scramling_enabled: true if TMDS scrambling is on */
bool scrambling_enabled;
```

Should be `@scrambling_enabled` (missing 'b').

**Minor: `drm_scdc_status_flags` struct fields have no kdoc.** The `drm_scdc_state` members are documented, but the nested `drm_scdc_status_flags` fields are not. Since these structs are in a public header and `drm_scdc_read_state` is exported, adding kdoc would be good practice.

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