Input: st1232 - add device tree support

This patch enables DT support for the st1232 driver
which is primarily used on the sh7372 Mackerel board.

[dtor@mail.ru: chnaged to use CONFIG_OF and of_match_ptr]
Signed-off-by: Magnus Damm <damm@opensource.se>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>