If sysfs registration fails all memory used by IOMMU is freed. This
happens after dma_ops initialization and the functions will access the
freed memory then.

Fix this by initializing dma_ops after the sysfs registration.
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>