[PATCH] USB: Improve Kconfig comment for mct_u232

Add a couple of supported devices into the help message.

It's a long story... I promised this comment changed to a user long ago,
so I'd like to have that promise kept. In reality though, nobody is
likely to read this anyway.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>