exfat: redefine DIR_DELETED as the bad cluster number

When a file or a directory is deleted, the hint for the cluster of
its parent directory in its in-memory inode is set as DIR_DELETED.
Therefore, DIR_DELETED must be one of invalid cluster numbers. According
to the exFAT specification, a volume can have at most 2^32-11 clusters.
However, DIR_DELETED is wrongly defined as 0xFFFF0321, which could be
a valid cluster number. To fix it, let's redefine DIR_DELETED as
0xFFFFFFF7, the bad cluster number.

Fixes: 1acf1a564b60 ("exfat: add in-memory and on-disk structures and headers")
Cc: [e-mail] # v5.7+
Reported-by: Yuezhang Mo <[e-mail]>
Signed-off-by: Sungjong Seo <[e-mail]>
Signed-off-by: Namjae Jeon <[e-mail]>

fs/exfat/exfat_fs.h

···
 #define ES_IDX_LAST_FILENAME(name_len)	\
 	(ES_IDX_FIRST_FILENAME + EXFAT_FILENAME_ENTRY_NUM(name_len) - 1)
 
-#define DIR_DELETED		0xFFFF0321
+#define DIR_DELETED		0xFFFFFFF7
 
 /* type values */
 #define TYPE_UNUSED		0x0000