AT24XX: Correct address calculation in Multi-Block-Read

drivers/mtd/at24xx.c

@@ -387,7 +387,8 @@ static ssize_t at24c_bread(FAR struct mtd_dev_s *dev, off_t startblock,
         }
 
       offset += priv->pagesize;
-    }
+      buffer += priv->pagesize;
+   }
 
 #if CONFIG_AT24XX_MTD_BLOCKSIZE > AT24XX_PAGESIZE
    return nblocks / (CONFIG_AT24XX_MTD_BLOCKSIZE / AT24XX_PAGESIZE);