Claude review: fbdev: wmt_ge_rops: use devm_platform_ioremap_resource()

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

Patch Review

**Bug: `regbase` left as ERR_PTR on probe failure**

When `devm_platform_ioremap_resource()` fails, it returns an ERR_PTR value which gets assigned to `regbase`. The function then returns the error code, but `regbase` is left holding a non-NULL error-pointer value. On a subsequent probe attempt (or re-probe), the single-instance guard at line 152:

```c
if (unlikely(regbase)) {
    WARN_ON(1);
    return -EBUSY;
}
```

will see the stale ERR_PTR as non-NULL, fire the WARN_ON, and return `-EBUSY` — permanently blocking the driver from ever probing successfully again.

Fix: reset `regbase` to NULL in the error path:

```c
regbase = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(regbase)) {
    int ret = PTR_ERR(regbase);
    regbase = NULL;
    return ret;
}
```

**Removal of `iounmap()` is correct** — `devm_platform_ioremap_resource()` registers a devres action that automatically unmaps on device removal, so the explicit `iounmap()` must go. Setting `regbase = NULL` in `remove()` is the right thing to do for the re-probe guard.

**Minor: no `dev_err` on failure** — The original code printed `"failed to map I/O memory"` on failure. `devm_platform_ioremap_resource()` does emit its own error messages internally, so dropping the explicit `dev_err` is fine.

**Overall:** The patch needs a v2 to fix the ERR_PTR-in-`regbase` issue on the error path. Otherwise the conversion is clean and correct.

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