Use the new of_get_compatible_child() helper to lookup the legacy
pwrlevels child node instead of using of_find_compatible_node(), which
searches the entire tree and thus can return an unrelated (i.e.
non-child) node.

This also addresses a potential use-after-free (e.g. after probe
deferral) as the tree-wide helper drops a reference to its first
argument (i.e. the probed device's node).

While at it, also fix the related child-node reference leak.

Fixes: e2af8b6b0ca1 ("drm/msm: gpu: Use OPP tables if we can")
Cc: stable <redacted>     # 4.12
Cc: Jordan Crouse <redacted>
Cc: Rob Clark <redacted>
Cc: David Airlie <redacted>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/gpu/drm/msm/adreno/adreno_gpu.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index da1363a0c54d..93d70f4a2154 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c

@@ -633,8 +633,7 @@ static int adreno_get_legacy_pwrlevels(struct device *dev)
        struct device_node *child, *node;
        int ret;

-       node = of_find_compatible_node(dev->of_node, NULL,
-               "qcom,gpu-pwrlevels");
+       node = of_get_compatible_child(dev->of_node, "qcom,gpu-pwrlevels");