exfat: remove duplicate write inode for extending dir/file

Since the timestamps need to be updated, the directory entries
will be updated by mark_inode_dirty() whether or not a new
cluster is allocated for the file or directory, so there is no
need to use __exfat_write_inode() to update the directory entries
when allocating a new cluster for a file or directory.

Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Reviewed-by: Andy Wu <Andy.Wu@sony.com>
Reviewed-by: Aoyama Wataru <wataru.aoyama@sony.com>
Reviewed-by: Daniel Palmer <daniel.palmer@sony.com>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>