dma: cpp41: make it compile with CONFIG_BUG=n

Before Randy figures out that this does not compile with CONFIG_BUG=n
here is a fix for it.

Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>