rpmsg: glink: Expose rpmsg name attr for glink

Expose the name field as an attr so clients listening to uevents for
rpmsg can identify the edge the events correspond to.

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/1593017121-7953-5-git-send-email-deesin@codeaurora.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>