dmaengine: ioat: Fix error handling path

If the last test in 'ioat_dma_self_test()' fails, we must release all
the allocated resources and not just part of them.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>