Rather than carrying a special purpose blocking notifier for glink_ssr
in remoteproc's qcom_common.c, move it into glink_ssr so allow wider
reuse of the common one.

The rpmsg glink header file is used in preparation for the next patch.
Acked-by: Chris Lew <clew@codeaurora.org>
Acked-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
Link: https://lore.kernel.org/r/20200423003736.2027371-3-bjorn.andersson@linaro.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>