Input: add support for OMAP4 keyboard controller

OMAP4 keyboard controller includes:
  - built-in scanning algorithm
  - debouncing feature

Driver implementation is based on matrix_keypad.c

Signed-off-by: Syed Rafiuddin <rafiuddin.syed@ti.com>
Signed-off-by: Abraham Arce <x0066660@ti.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>