soc: qcom: geni: Fix NULL pointer dereference

pdev struct doesn't exits for the devices whose status are disabled
from DT node, in such cases NULL is returned from 'of_find_device_by_node'
Later when we try to get drvdata from pdev struct NULL pointer dereference
is triggered.

Add a NULL check for return values to fix the issue.

We were hitting this issue when one of QUP is disabled.
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Fixes: 048eb908 ("soc: qcom-geni-se: Add interconnect support to fix earlycon crash")
Reported-by: Sai Prakash Ranjan <saipraka@codeaurora.org>
Signed-off-by: Akash Asthana <akashast@codeaurora.org>
Link: https://lore.kernel.org/r/1594996342-26964-1-git-send-email-akashast@codeaurora.org
[bjorn: s/wrapper_pdev/pdev/]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/soc/qcom/qcom-geni-se.c

@@ -817,6 +817,7 @@ EXPORT_SYMBOL(geni_icc_disable);
 
 void geni_remove_earlycon_icc_vote(void)
 {
+	struct platform_device *pdev;
 	struct geni_wrapper *wrapper;
 	struct device_node *parent;
 	struct device_node *child;
@@ -829,7 +830,12 @@ void geni_remove_earlycon_icc_vote(void)
 	for_each_child_of_node(parent, child) {
 		if (!of_device_is_compatible(child, "qcom,geni-se-qup"))
 			continue;
-		wrapper = platform_get_drvdata(of_find_device_by_node(child));
+
+		pdev = of_find_device_by_node(child);
+		if (!pdev)
+			continue;
+
+		wrapper = platform_get_drvdata(pdev);
 		icc_put(wrapper->to_core.path);
 		wrapper->to_core.path = NULL;