rpmsg: glink: Use complete_all for open states

rpmsg: glink: Use complete_all for open states

The open_req and open_ack completion variables are the state variables
to represet a remote channel as open. Use complete_all so there are no
races with waiters and using completion_done.

Signed-off-by: Chris Lew <clew@codeaurora.org>
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>
Signed-off-by: Deepak Kumar Singh <deesin@codeaurora.org>
Link: https://lore.kernel.org/r/1593017121-7953-2-git-send-email-deesin@codeaurora.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>