dt-bindings: rtc: at91: Add SAMA7G5 compatible strings list

Add compatible strings list for SAMA7G5.

Signed-off-by: Sergiu Moga <sergiu.moga@microchip.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220304161159.147784-5-sergiu.moga@microchip.com