Maybe update the minextblks in wrong way?

[Hongbo Li]

Hi Sandeep,
   The consecutive chunks will be merged if possible, but after commit 
545988a65131 ("erofs-utils: lib: Fix calculation of minextblks when 
working with sparse files"), the @minextblks will be updated into a 
smaller value even the chunks are consecutive by blobchunks.c:379. I 
think maybe the last operation that updates @minextblks is unnecessary, 
since this value would have already been adjusted earlier when handling 
discontinuous chunks. Likes:

```
--- a/lib/blobchunk.c
+++ b/lib/blobchunk.c
@@ -376,7 +376,6 @@ int erofs_blob_write_chunked_file(struct erofs_inode 
*inode, int fd,
                 *(void **)idx++ = chunk;
                 lastch = chunk;
         }
-       erofs_update_minextblks(sbi, interval_start, pos, &minextblks);
         inode->datalayout = EROFS_INODE_CHUNK_BASED;
         free(chunkdata);
         return erofs_blob_mergechunks(inode, chunkbits,

```
This way can reduces the chunk index array's size. And what about your 
opinion?

Thanks,
Hongbo