rpmsg: glink: Put an extra reference during cleanup

In a remote processor crash scenario, there is no guarantee the remote
processor sent close requests before it went into a bad state. Remove
the reference that is normally handled by the close command in the
so channel resources can be released.

Fixes: b4f8e52b

 ("rpmsg: Introduce Qualcomm RPM glink driver")
Cc: stable@vger.kernel.org
Tested-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Chris Lew <clew@codeaurora.org>
Reported-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>