dmaengine: ti: k3-udma: Use udma_chan instead of tchan/rchan for IO functions

Move the uc->tchan/rchan checks to the IO wrappers itself instead of
calling the functions with tchan/rchan directly.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Link: https://lore.kernel.org/r/20200707102352.28773-6-peter.ujfalusi@ti.comSigned-off-by: Vinod Koul <vkoul@kernel.org>