drivers/bch: delay the sector flush

Delay the sector flush to avoid multiple earse/write operations in sequence write

Change-Id: If4331b7fc8d2c2061325533212b28e826141b411
Signed-off-by: chao.an <anchao@xiaomi.com>

drivers/bch/bchlib_write.c

@@ -184,14 +184,5 @@ ssize_t bchlib_write(FAR void *handle, FAR const char *buffer, size_t offset,
       byteswritten += len;
     }
 
-  /* Finally, flush any cached writes to the device as well */
-
-  ret = bchlib_flushsector(bch);
-  if (ret < 0)
-    {
-      ferr("ERROR: Flush failed: %d\n", ret);
-      return ret;
-    }
-
   return byteswritten;
 }