fat: expand a slightly out-of-date comment

The file namei.c seems to have been renamed to namei_msdos.c, so I decided
to update the comment with the correct name, and expand it a bit to tell
the reader what to look for.

Link: http://lkml.kernel.org/r/20180928194947.23932-1-mihir@cs.utexas.edu
Signed-off-by: Mihir Mehta <mihir@cs.utexas.edu>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/fat/dir.c

@@ -369,7 +369,9 @@ static int fat_parse_short(struct super_block *sb,
 	}
 
 	memcpy(work, de->name, sizeof(work));
-	/* see namei.c, msdos_format_name */
+	/* For an explanation of the special treatment of 0x05 in
+	 * filenames, see msdos_format_name in namei_msdos.c
+	 */
 	if (work[0] == 0x05)
 		work[0] = 0xE5;