dmaengine: ste_dma: fix incompatible pointer type warns

drivers/dma/ste_dma40.c:2627:3: warning: 'return' with a value, in function returning void [enabled by default]
drivers/dma/ste_dma40.c: In function 'd40_ops_init':
drivers/dma/ste_dma40.c:2869:28: warning: assignment from incompatible pointer type [enabled by default]

The function prototype expects return type 'int' whereas these where void

Signed-off-by: Vinod Koul <vinod.koul@intel.com>