Use proper compatible strings for SAMA5D2's RTC IPs. This is necessary
for configuring wakeup sources for ULP1 PM mode.

Fixes: d7484f5c ("ARM: at91: pm: configure wakeup sources for ULP1 mode")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220523092421.317345-2-claudiu.beznea@microchip.com