regulator: remove unnecessary of_node_get() to parent

These of_node_get() were added to balance refcount decrements inside of
of_find_node_by_name().
See: commit c92f5dd2c42f ("regulator: Add missing of_node_put()")

However of_find_node_by_name() was then replaced by of_get_child_by_name(),
which doesn't call of_node_put() against its input parameter.

So, need to remove these unnecessary of_node_get() calls.

Signed-off-by: Guodong Xu <guodong.xu@linaro.org>
Reviewed-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>