arm: dts: iot2050: Use the auto generator nodes for fdt

arm: dts: iot2050: Use the auto generator nodes for fdt

Refactor according to the entry `fit: Entry containing a FIT` of
document tools/binman/README.entries.

As the generator uses the device tree name for the config description,
board_fit_config_name_match requires a small adjustment as well.

Signed-off-by: Su Baocheng <baocheng.su@siemens.com>
[Jan: re-add now required CONFIG_OF_LIST, update config matching]
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Simon Glass <sjg@chromium.org>