MLK-21461: ASoC: fsl_rpmsg_i2s: clear buffer pointer in i2s_send_message

MLK-21461: ASoC: fsl_rpmsg_i2s: clear buffer pointer in i2s_send_message

Reset the buffer pointer to be zero in i2s_send_message, actully we have
set the buffer pointer to be zero in imx_rpmsg_terminate_all.
But if there is timer task (I2S_TX_POINTER) queued in queue, after it is
executed the buffer pointer will be changed, this is timing issue that
the task in the queue is delayed. so need to reset it with TERMINATE
command.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
(cherry picked from commit 0a07dd454cbf85744677812e53fc5e86a48706bf)