dmaengine: ipu: Consolidate duplicated irq handlers

The functions irq_irq_err and ipu_irq_fn are identical plus/minus the
comments. Remove one.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Vinod Koul <vinod.koul@intel.com>