dmaengine: ti: k3-udma: Use the channel direction in pause/resume functions

It should be possible to pause, resume and check the pause state of a
channel even if we do not have active transfer.

udma_is_chan_paused() can trigger NULL pointer reference in it's current
form when the status is checked while uc->desc is NULL.

Fixes: 25dcb5dd ("dmaengine: ti: New driver for K3 UDMA")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200214091441.27535-6-peter.ujfalusi@ti.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>