exfat: add error check when updating dir-entries

Add error check when synchronously updating dir-entries.

Suggested-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Tetsuhiro Kohada <kohada.t2@gmail.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Git-commit: 8b0c471773819c8201dc0b0123e1580639ee1570
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: lixiang <lixiang@codeaurora.org>