exfat: fix refcount leak in exfat_find

In the Linux kernel, the following vulnerability has been resolved:

exfat: fix refcount leak in exfat_find

Fix refcount leaks in exfat_find related to exfat_get_dentry_set.

Function exfat_get_dentry_set would increase the reference counter of es->bh on success. Therefore, exfat_put_dentry_set must be called after exfat_get_dentry_set to ensure refcount consistency. This patch relocate two checks to avoid possible leaks.