rtc: Add driver for SD2405AL

rtc: Add driver for SD2405AL

Add support for the DFRobot SD2405AL I2C RTC Module.

Datasheet:
	https://image.dfrobot.com/image/data/TOY0021/SD2405AL%20datasheet%20(Angelo%20v0.1).pdf

Product:
	https://www.dfrobot.com/product-1600.html

To instantiate (assuming device is connected to I2C-1)
as root:
	echo sd2405al 0x32 > /sys/bus/i2c/devices/i2c-1/new_device
as user:
	echo 'sd2405al 0x32' | sudo tee /sys/class/i2c-adapter/i2c-1/new_device

The driver is tested with:
	+ hwclock
	+ tools/testing/selftests/rtc/setdate
	+ tools/testing/selftests/rtc/rtctest

Reviewed-by: Csókás Bence <csokas.bence@prolan.hu>
Signed-off-by: Tóth János <gomba007@gmail.com>
Link: https://lore.kernel.org/r/20240830-rtc-sd2405al-v7-1-2f7102621b1d@gmail.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>