rpmsg: glink: Do a mbox_free_channel in remove
mbox_request_channel is done in probe, so free the channel in remove.
Acked-by: Arun Kumar Neelakantam <aneela@codeaurora.org>
Signed-off-by: Sricharan R <sricharan@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>