Input: cyapa - add power management interfaces support for the device

Add suspend_scanrate_ms power management interfaces in device's
power group, so users or applications can control the power management
strategy of trackpad device according to their requirements.

Signed-off-by: Dudley Du <dudl@cypress.com>
Tested-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>