qcow2: Remove unused struct QCowCreateState

The only user went away five years ago with commit a942073 ('qcow2:
Simplify image creation'). It's about time to remove it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

block/qcow2.h

@@ -275,17 +275,6 @@ typedef struct BDRVQcowState {
     bool cache_discards;
 } BDRVQcowState;
 
-/* XXX: use std qcow open function ? */
-typedef struct QCowCreateState {
-    int cluster_size;
-    int cluster_bits;
-    uint16_t *refcount_block;
-    uint64_t *refcount_table;
-    int64_t l1_table_offset;
-    int64_t refcount_table_offset;
-    int64_t refcount_block_offset;
-} QCowCreateState;
-
 struct QCowAIOCB;
 
 typedef struct Qcow2COWRegion {