dt-bindings: rtc: Add support for SD2405AL.

Add the necessary documentation for SD2405AL.
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Tóth János <gomba007@gmail.com>
Link: https://lore.kernel.org/r/20240830-rtc-sd2405al-v7-2-2f7102621b1d@gmail.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/trivial-rtc.yaml

@@ -38,6 +38,8 @@ properties:
       - dallas,ds1672
       # Extremely Accurate I²C RTC with Integrated Crystal and SRAM
       - dallas,ds3232
+      # SD2405AL Real-Time Clock
+      - dfrobot,sd2405al
       # EM Microelectronic EM3027 RTC
       - emmicro,em3027
       # I2C-BUS INTERFACE REAL TIME CLOCK MODULE