soc: qcom: glink: make glink_tx() safe in atomic context

In the RPM suspend use case, glink_tx() is called with the
GLINK_TX_SINGLE_THREADED option in atomic context, but the entire code
path is not atomic safe.

Make glink_tx() with the GLINK_TX_SINGLE_THREADED option safe in atomic
context.

Change-Id: Ifbc1a240bedbeecba9c5d8f4e1d61edf0cdfc5e5
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>
Signed-off-by: Eric Holmberg <eholmber@codeaurora.org>