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>