dmaengine: s3c24xx: explicitly freeup irq

dmaengine device should explicitly call devm_free_irq() when using
devm_request_irq().

The irq is still ON when devices remove is executed and irq should be
quiesced before remove is completed.

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>