Input: add twl4030_keypad driver

Add a driver for the keypad controller on TWL4030 family chips.
These support up to an 8x8 key matrix.  The TWL4030 multifunction
chips are mostly used on OMAP3 (or OMAP 2430) based boards.

[dtor@mail.ru: switch to matrix-keypad framework, fix changing
keymap from userspace]
Reviewed-by: Trilok Soni <soni.trilok@gmail.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>