ARM: ux500: Supply the STMPE keypad Device Tree node to the STUIB DT

This patch allows the STMPE keypad driver to be successfully probed
and initialised during a Device Tree enabled boot sequence. It
contains all of the required properties needed to setup and map
each key on the 6x3 keypad located on the ST User Interface Board.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>