block.h: bdrv_create2 doesn't exist any more

The bdrv_create2 implementation has disappeared long ago. Remove its
prototype from the header file, too.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block.h

@@ -57,10 +57,6 @@ BlockDriver *bdrv_find_format(const char *format_name);
 BlockDriver *bdrv_find_whitelisted_format(const char *format_name);
 int bdrv_create(BlockDriver *drv, const char* filename,
     QEMUOptionParameter *options);
-int bdrv_create2(BlockDriver *drv,
-                 const char *filename, int64_t size_in_sectors,
-                 const char *backing_file, const char *backing_format,
-                 int flags);
 BlockDriverState *bdrv_new(const char *device_name);
 void bdrv_delete(BlockDriverState *bs);
 int bdrv_file_open(BlockDriverState **pbs, const char *filename, int flags);