Implement PM runtime autosuspend support to prepare for adding handling to
clear stuck last pressed key in the following patches. The hardware has
support for autoidle and can wake up to keypress events.

Let's also update omap4_keypad_probe() to use dev instead of &pdev->dev
since we already have it from the earlier changes.
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/X/vqCs5/EDURprAJ@atomide.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>