ARM: at91: pm: use proper compatibles for sama7g5's rtc and rtt

Use proper compatible strings for SAMA7G5's RTC and RTT IPs. These are
necessary for configuring wakeup sources for ULP1 PM mode.

Fixes: 6501330f

 ("ARM: at91: pm: add pm support for SAMA7G5")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220523092421.317345-4-claudiu.beznea@microchip.com