Check that asynchronous (DMA) submission succeeds (Ian Jackson).

If it does not, abort the command immediately rather than dropping
it on the floor.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5369 c046a42c-6fe2-441c-8c8c-71466251a162
