ARM: at91: pm: use proper compatibles for sam9x60's rtc and rtt

Use proper compatible strings for SAM9X60's RTC and RTT IPs. These are
necessary for configuring wakeup sources for ULP1 PM mode.

Fixes: eaedc0d3

 ("ARM: at91: pm: add ULP1 support for SAM9X60")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220523092421.317345-3-claudiu.beznea@microchip.com