ARM: dts: microchip: sam9x60: Fix rtc/rtt clocks

ARM: dts: microchip: sam9x60: Fix rtc/rtt clocks

The RTC and RTT peripherals use the timing domain slow clock (TD_SLCK),
sourced from the 32.768 kHz crystal oscillator or slow rc oscillator.

The previously used Monitoring domain slow clock (MD_SLCK) is sourced
from an internal RC oscillator which is most probably not precise enough
for real time clock purposes.

Fixes: 1e5f532c2737 ("ARM: dts: at91: sam9x60: add device tree for soc and board")
Fixes: 5f6b33f46346 ("ARM: dts: sam9x60: add rtt")
Signed-off-by: Alexander Dahl <ada@thorsis.com>
Link: https://lore.kernel.org/r/20240821055136.6858-1-ada@thorsis.com
[claudiu.beznea: removed () around the last commit description paragraph,
 removed " in front of "timing domain slow clock", described that
 TD_SLCK can also be sourced from slow rc oscillator]
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>