virtio-blk: Treat read/write beyond end as invalid

virtio-blk: Treat read/write beyond end as invalid

The block layer fails such reads and writes just fine.  However, they
then get treated like valid operations that fail: the error action
gets executed.  Unwanted; reporting the error to the guest is the only
sensible action.

Reject them before passing them to the block layer.  This bypasses the
error action and I/O accounting.

Signed-off-by: Markus Armbruster <[email protected]>
Reviewed-by: Fam Zheng <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>