s390/virtio_ccw: use DMA handle from DMA API

Change and use ccw_device_dma_zalloc() so it returns a virtual address like
before, which can be used to access data. However also pass a new dma32_t
pointer type handle, which correlates to the returned virtual address.
This pointer is used to directly pass/set the DMA handle as returned by the
DMA API.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>