qapi/block-core: Fix BlockdevOptionsNvmeIoUring @path description

qapi/block-core: Fix BlockdevOptionsNvmeIoUring @path description

The nvme-io_uring BlockDriver's path option must point at the character
device of an NVMe namespace, not at an image file.

Fixes: fd66dbd424f5 ("blkio: add libblkio block driver")
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Alberto Faria <afaria@redhat.com>
Message-Id: <20221108142347.1322674-1-afaria@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>