dmaengine: pch_dma: fix memory leak on failure path in pch_dma_probe()

Memory allocated for pch_dma is not deallocated in case of failure
in pch_dma_probe().

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>