arm64: allwinner: h6: add PCF8563 RTC on Pine H64 board

Pine H64 board has a PCF8563 dedicated RTC connected to its R_I2C bus.

Enable the R_I2C bus and add the RTC to the device tree.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>