powerpc/windfarm: Use for_each_node_by_type() macro

Use for_each_node_by_type() macro instead of open coding it.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --cc drivers/macintosh/windfarm_pm112.c
Simple merge

diff --cc drivers/macintosh/windfarm_pm72.c
Simple merge

diff --cc drivers/macintosh/windfarm_rm31.c
Simple merge