of/fdt: declared return type does not match actual return type

The commit 649cab56 (“of: properly check for error returned
by fdt_get_name()”) changed the return value type from bool to int,
but forgot to change the return value simultaneously.

populate_node was only called in unflatten_dt_nodes, and returns
with values greater than or equal to 0 were discarded without further
processing. Considering that return 0 usually indicates success,
return 0 instead of return true.

Fixes: 649cab56 (“of: properly check for error returned by fdt_get_name()”)
Signed-off-by: Xu Qiang <xuqiang36@huawei.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220801120506.11461-2-xuqiang36@huawei.com