ARM: at91: pm: add sama7g5 ddr controller

Add SAMA7G5 DDR controller to the list of DDR controller compatibles.
At the moment there is no standby support. Adapt the code for this.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210415105010.569620-18-claudiu.beznea@microchip.com