dmaengine: ti: k3-udma: Fix BCDMA for case w/o BCHAN

Reusing loop iterator fails if BCHAN is not present as iterator is
uninitialized

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Link: https://lore.kernel.org/r/20221213164304.1126945-3-vigneshr@ti.com


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