scripts: remove boards_legacy sub-folder from list_boards.py

Fixes: #69785

The boards_legacy sub-folder was temporarily introduce in collab-hwm
branch during porting to HWMv2.

This should have been removed before merging collab-hwm to main as it
prevent looking up boards in oot roots.

Removing the temporary sub-folder for HWMv2.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
diff --git a/scripts/list_boards.py b/scripts/list_boards.py
index 9a0757c..03b1ada 100755
--- a/scripts/list_boards.py
+++ b/scripts/list_boards.py
@@ -156,17 +156,17 @@
     boards = root / 'boards'
 
     for arch in arches:
-        if not (boards / "boards_legacy" / arch).is_dir():
+        if not (boards / arch).is_dir():
             continue
 
-        for maybe_board in (boards / "boards_legacy" / arch).iterdir():
+        for maybe_board in (boards / arch).iterdir():
             if not maybe_board.is_dir():
                 continue
             if board_dir is not None and board_dir != maybe_board:
                 continue
             for maybe_defconfig in maybe_board.iterdir():
                 file_name = maybe_defconfig.name
-                if file_name.endswith('_defconfig'):
+                if file_name.endswith('_defconfig') and not (maybe_board / BOARD_YML).is_file():
                     board_name = file_name[:-len('_defconfig')]
                     ret[arch].add(Board(board_name, maybe_board, 'v1', arch=arch))