xen/blkback: Move the check for misaligned I/O once more.

The commit 976222e05ea5a9959ccf880d7a24efbf79b3c6cf

    xen/blkback: Move the check for misaligned I/O higher.

moved it a bit to high. The preq->vbdev was not set, so the
check for misaligned I/O would cause a NULL pointer derefence.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
1 file changed