rpmsg: glink-smem: Name the edge based on parent remoteproc

Naming the glink edge device on the parent of_node short name causes
collisions when multiple remoteproc instances with only different unit
address are described on the platform_bus in DeviceTree.

Base the edge's name on the parent remoteproc's name instead, to ensure
that it's unique.

Reviewed-by: Niklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>