power: reset: at91-sama5d2_shdwc: add support for sama7g5

Add support for SAMA7G5 by adding proper struct reg_config structure
and since SAMA7G5 is not currently on LPDDR setups the commit also
avoid the mapping of DDR controller.

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