arch/sh/drivers/dma/{dma-g2,dmabrg}.c: ensure arguments to request_irq and free_irq are compatible

Convert calls to free_irq so that the second argument is the same as the
last argument of the corresponding call to request_irq.  Without this
property, free_irq does nothing.

In the case of dmabrg.c the change is merely cosmetic - changing 0 to NULL.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>