dma: mpc512x: fix freeing resources in mpc_dma_probe() and mpc_dma_remove()

Fix mpc_dma_probe() error path and mpc_dma_remove(): manually free IRQs and
dispose IRQ mappings before devm_* takes care of other resources.
Moreover replace devm_request_irq() with request_irq() since there is no need
to use it because the original code always frees IRQ manually with
devm_free_irq(). Replace devm_free_irq() with free_irq() accordingly.

Signed-off-by: Alexander Popov <a13xp0p0v88@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>