soc: qcom: glink_probe: use lock while sending ssr notification

In ssr handling of remote subsystem down, all rpmsg devices are removed
for that edge. If at the same time ssr down is received for other remote
subsystem, it may try to notify already down remote and end up using
invalid rpmsg device which results in use after free.

Store device state in ssr context and update this with holding a lock.
SSR notification function should also use the same lock and perform
check for validity of rpmsg device.

CRs-Fixed: 2580433
Change-Id: I339e228a527f7b6a737944d8e9e53caa31992914
Signed-off-by: Deepak Kumar Singh <deesin@codeaurora.org>