exfat: move free cluster out of exfat_init_ext_entry()

exfat_init_ext_entry() is an init function, it's a bit strange
to free cluster in it. And the argument 'inode' will be removed
from exfat_init_ext_entry(). So this commit changes to free the
cluster in exfat_remove_entries().

Code refinement, no functional changes.

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: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>