MLK-9987: Input: imx_keypad: Fix suspend/resume while keypad is pressed

Since commit commit 560a64749d1dd0ff ("ENGR00318936-2 input: keyboard: imx:
remove usless release interrupt enabled) the following problem happens:

- Keep any keypad key pressed
- Enter low power mode via "echo mem > /sys/power/state"
- Then we are no longer able to wake-up the system via the keypad

The reason for this behaviour is that the KRIE (Release Interrupt) is not
enabled.

In order to fix this problem, we should enable KRIE when a key is pressed
(KPKD bit is set) or enable KDIE when no key is pressed (KPKR is set).

This way we will always have a valid source of keypad interrupt no matter if
the system entered low power mode while a keypad key was pressed or not.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
(cherry picked from commit 5a7ab47e67d1045cb2f5d408c112617dff48dee2)