dmaengine: cppi41: Remove isr callback from glue layer

All the platform code to manage IRQ has been moved to MUSB,
and now the interrupt handler is completely generic.
Remove the isr callback that is not useful anymore.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>