soc: qcom: Use syncronization while freeing the qmi_client data

Potential use after free possibility when trying to access qmi client
data in the ssr notification and root pd_down notification handling.

CRs-Fixed: 1074483
Change-Id: I5390810861dbc1da368757df2b20e5daa35bd081
Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>