When devm_kcalloc fails, it forgets to call edma_free_slot.
Replace direct return with failure handler to fix it.

Fixes: 1be5336b ("dmaengine: edma: New device tree binding")
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Link: https://lore.kernel.org/r/20191118073802.28424-1-hslester96@gmail.comSigned-off-by: Vinod Koul <vkoul@kernel.org>