Move block dma helpers aiocb to store dma state (Avi Kivity)

Move block dma helpers aiocb to store dma state (Avi Kivity)

Use the dedicated dma aiocb to store intermediate state for dma block
transactions.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6874 c046a42c-6fe2-441c-8c8c-71466251a162

[ Backported from 6bbff9a0b495918309074ac60375be5f9dc868b3
  by Stefano Stabellini. ]

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
(cherry picked from commit 36c862ce5f43949aaa5885d5682f074d2cb4966f)