rpmsg: glink: Fix use after free in open_ack TIMEOUT case

Extra channel reference put when remote sending OPEN_ACK after timeout
causes use-after-free while handling next remote CLOSE command.

Remove extra reference put in timeout case to avoid use-after-free.

Fixes: b4f8e52b

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