scripts: test_plan: Fix issue introduced in 3f77560
The rewrite by ruff seems to wrongly pass a single argument to filter(),
as seen in the logs:
```
f.process()
File "/home/runner/work/zephyr/zephyr/zephyr/./scripts/ci/test_plan.py",
line 145, in process
self.find_boards()
File "/home/runner/work/zephyr/zephyr/zephyr/./scripts/ci/test_plan.py",
line 292, in find_boards
self.resolved_files.extend(list(filter(resolved_filter)))
^^^^^^^^^^^^^^^^^^^^^^^
TypeError: filter expected 2 arguments, got 1
```
Split things up properly to avoid this.
Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
1 file changed
