fat: fix bug in enforcing Long File Name length

Since '*outlen' is initialized to zero, it is currently possible to
create a filename of length (FAT_LFN_LEN + 1) when utf8 is not enabled.
To enforce the FAT_LFN_LEN limit, we must perform one less iteration.

Signed-off-by: Namjae Jeon <[e-mail]>
Signed-off-by: Ravishankar N <[e-mail]>
Acked-by: OGAWA Hirofumi <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/fat/namei_vfat.c

···
 		op = &outname[*outlen * sizeof(wchar_t)];
 	} else {
 		for (i = 0, ip = name, op = outname, *outlen = 0;
-			 i < len && *outlen <= FAT_LFN_LEN;
+			 i < len && *outlen < FAT_LFN_LEN;
 			 *outlen += 1) {
 			if (escape && (*ip == ':')) {
 				if (i > len - 5)