soc: qcom: spss_utils: handle ssr after fota

After SPU's firmware was updated,
prevent SSR from happening until getting
a message from userspace that update is finished.
Need to Avoid SSR because PIL would load old images from /firmware_mnt.

Change-Id: I4b07e2e886e26a928faeae0c6f4f790dd01c645f
Signed-off-by: Dan Bar-On <dbaron@codeaurora.org>