V4L/DVB (11084): au0828: add entry for undefined input type

For the sake of completeness, include the "undefined" input type enumeration,
even though there is no path that can actually call it.

Thanks to Mauro Carvalho Chehab <mchehab@infradead.org> for pointing this out.

Signed-off-by: Devin Heitmueller <dheitmueller@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>