dmaengine: ti: k3-udma: Switch to k3_ringacc_request_rings_pair

We only request ring pairs via K3 DMA driver, switch to use the new
k3_ringacc_request_rings_pair() to simplify the code.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>