scripts: remove boards_legacy sub-folder from list_boards.py

  set(OPERATION WRITE)

  foreach(root ${kconfig_soc_root})

    file(APPEND ${soc_defconfig_file}

         "osource \"${root}/soc/soc_legacy/$(ARCH)/*/Kconfig.defconfig\"\n")

         "osource \"${root}/soc/$(ARCH)/*/Kconfig.defconfig\"\n")

    file(${OPERATION} ${KCONFIG_BINARY_DIR}/soc/Kconfig.soc.choice

         "osource \"${root}/soc/soc_legacy/$(ARCH)/*/Kconfig.soc\"\n"

         "osource \"${root}/soc/$(ARCH)/*/Kconfig.soc\"\n"

    )

    file(${OPERATION} ${KCONFIG_BINARY_DIR}/soc/Kconfig.soc.arch

         "osource \"${root}/soc/soc_legacy/$(ARCH)/Kconfig\"\n"

         "osource \"${root}/soc/soc_legacy/$(ARCH)/*/Kconfig\"\n"

         "osource \"${root}/soc/$(ARCH)/Kconfig\"\n"

         "osource \"${root}/soc/$(ARCH)/*/Kconfig\"\n"

    )

    set(OPERATION APPEND)

  endforeach()

    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))

# This loads custom SoC root Kconfig (only available if custom SoC root are defined)

osource "$(KCONFIG_BINARY_DIR)/soc/Kconfig.soc.arch"

# This loads Zephyr base SoC Kconfigs

osource "soc/soc_legacy/$(ARCH)/*/Kconfig"