input: kbd_matrix: add power management support

Add power management support to the keyboard matrix library. This
provides a generic pm_action function that changes the keyboard matrix
scan in two places when suspended:
- reset the state to 0 for all columns
- do not enable key press detection

This ensures that any key that was pressed when the device is suspended
is released, and no other scan happens until the device is resumed.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>