soc: qcom: ssr: Check the subsystem state before initiating SSR

In the case when subsystem restart is triggered on a subsystem
which is being shutdown, there might be a race condition which
could involve the SSR framework trying to restart a subsystem
which is already shutdown. Print a warning and return from the
SSR function if this is the case.

Change-Id: I38083822db598e7b292bcf3b9e187a9f56d48bbb
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>