soc: qcom: pmic_glink: don't traverse clients list without a lock

Take the client_lock before traversing the clients list at the
pmic_glink_state_notify_clients() function. This is required to keep the
list traversal safe from concurrent modification.

Fixes: 58ef4ece

 ("soc: qcom: pmic_glink: Introduce base PMIC GLINK driver")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Andrew Halaney <ahalaney@redhat.com>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Tested-by: Xilin Wu <wuxilin123@gmail.com> # on QCS8550 AYN Odin 2
Link: https://lore.kernel.org/r/20240403-pmic-glink-fix-clients-v2-1-aed4e02baacc@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>