Input: omap-keypad - use bitfiled instead of hardcoded values

Use bitfiled instead of hardcoded values to set KBD_CTRL, use BIT macro,
remove unused defines.

Signed-off-by: Illia Smyrnov <illia.smyrnov@ti.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>