soc: qcom: pmic_glink: Switch using rpmsg_send() to avoid random Tx failure

When the remote subsystem is bought out of reset and PMIC Glink
channel is opened up, PMIC Glink rpmsg driver is probed after
which it instantiates all its child(client) devices. During its
probe, these client devices start communicating to the remote
subsystem over PMIC Glink channel. However, there is a race
condition observed randomly where a transaction from a client is
failing because rpmsg_trysend() couldn't send the message to the
remote endpoint as the remote subsystem haven't queued up all Rx
intents. To make the communication robust for clients, switch to
use rpmsg_send() instead of rpmsg_trysend() which will wait until
the Rx intents are queued up.

Change-Id: Ia632efb420fa76face0aae6e039c3dcbf3e9517a
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>