power: reset: at91-reset: introduce ramc_lpr to struct at91_reset

Introduce ramc_lpr to struct at91_reset. This will lead to the
unification of at91sam9260_restart() and at91sam9g45_restart().

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>