ARM: at91: pm: add support for per SoC wakeup source configuration

Add support for per SoC wakeup source configuration. In this way
we could have per SoC wakeup sources, shutdown controller and power
management controller configurations for ULP1 power management mode.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>