block: add BdrvDirtyBitmap documentation

 *     or enabled. A frozen bitmap can only abdicate() or reclaim().

 */

struct BdrvDirtyBitmap {

    HBitmap *bitmap;

    BdrvDirtyBitmap *successor;

    int64_t size;

    char *name;

    bool disabled;

    HBitmap *bitmap;            /* Dirty sector bitmap implementation */

    BdrvDirtyBitmap *successor; /* Anonymous child; implies frozen status */

    char *name;                 /* Optional non-empty unique ID */

    int64_t size;               /* Size of the bitmap (Number of sectors) */

    bool disabled;              /* Bitmap is read-only */

    QLIST_ENTRY(BdrvDirtyBitmap) list;

};