dma: ti: k3-udma: Fix build warnings when building for 32 bit platforms

Cast pointers properly so as to avoid warnings when driver is built for
32 bit platforms

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>