block/qapi: Set s->device in bdrv_query_stats()

block/qapi: Set s->device in bdrv_query_stats()

This is the only instance of bdrv_query_blk_stats() accessing anything
in the BlockStats structure other than s->stats, so let us move it to
its caller (where it makes just as much sense) allowing us to make
bdrv_query_blk_stats() take a pointer to the BlockDeviceStats instead of
BlockStats.

Signed-off-by: Max Reitz <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>