linux-phytec-fsl

MLK-9768: dma: imx-sdma: fix UART loopback random failed

For UART, we need use old chn_real_count to know the real rx count even in
cylic dma mode, because UART driver use cyclic mode to increase performance
without any data loss.

Signed-off-by: Robin Gong <b38343@freescale.com>
(cherry picked from commit 398cee2ad110c4f183e553af0564fbdcbe8548cb)