exfat: improve error code handling in exfat_find_empty_entry()

Change the type of 'ret' from unsigned int to int in
exfat_find_empty_entry(). Although the implicit type conversion
(int -> unsigned int -> int) does not cause actual bugs in
practice, using int directly is more appropriate for storing
error codes returned by exfat_alloc_cluster().

This improves code clarity and consistency with standard error
handling practices.

Signed-off-by: Haotian Zhang <vulab@iscas.ac.cn>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Author: ISCAS-Vulab

fs/exfat/namei.c

@@ -304,8 +304,8 @@ int exfat_find_empty_entry(struct inode *inode,
 		struct exfat_chain *p_dir, int num_entries,
 		struct exfat_entry_set_cache *es)
 {
-	int dentry;
-	unsigned int ret, last_clu;
+	int dentry, ret;
+	unsigned int last_clu;
 	loff_t size = 0;
 	struct exfat_chain clu;
 	struct super_block *sb = inode->i_sb;