dm: core: fix introduce uclass_get_device_by_of_path

Correct the function documentation.

Fixes: ca031c08 ("dm: core: introduce uclass_get_device_by_of_path()")
Reported-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>