exfat: fix range validation error in alloc and free cluster

There is check error in range condition that can never be entered
even with invalid input.
Replace incorrent checking code with already existing valid checker.

Signed-off-by: hyeongseok.kim <hyeongseok@gmail.com>
Acked-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Git-commit: a949824f01f3b39f737d77aed6cba47aced09319
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


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