Input: add driver for stowaway serial keyboards

Add support for stowaway and stowaway compatible (eg. dicota inutPDA)
serial keyboards. Reported to work on palm zire71 and palm tungsten T3.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>