mm: shmem: use signed int for version handling in casefold option

Fixes an issue where the use of an unsigned data type in
`shmem_parse_opt_casefold()` caused incorrect evaluation of negative
conditions.

Link: https://lkml.kernel.org/r/20250111-unsignedcompare1601569-v3-1-c861b4221831@gmail.com
Fixes: 58e55ef ("tmpfs: Add casefold lookup support")
Reviewed-by: André Almeida <andrealmeid@igalia.com>
Reviewed-by: Gabriel Krisman Bertazi <gabriel@krisman.be>
Signed-off-by: Karan Sanghavi <karansanghvi98@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Hugh Dickens <hughd@google.com>
Cc: Shuah khan <skhan@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: NaRaK-AK47

mm/shmem.c

@@ -4368,7 +4368,7 @@ static int shmem_parse_opt_casefold(struct fs_context *fc, struct fs_parameter *
 				    bool latest_version)
 {
 	struct shmem_options *ctx = fc->fs_private;
-	unsigned int version = UTF8_LATEST;
+	int version = UTF8_LATEST;
 	struct unicode_map *encoding;
 	char *version_str = param->string + 5;