convert xen-blkfront to atomic queue limit updates v2

[Christoph Hellwig <hch@xxxxxx>]

Hi all,

this series converts xen-blkfront to the new atomic queue limits update
API in the block tree.  I don't have a Xen setup so this is compile
tested only.

Changes since v1:
 - constify the info argument to blkif_set_queue_limits
 - remove a spurious word from a commit message

Diffstat:
 xen-blkfront.c |   53 +++++++++++++++++++++++++++--------------------------
 1 file changed, 27 insertions(+), 26 deletions(-)