rtc: rx6110: add ACPI bindings to I2C

This allows the RX6110 driver to be automatically assigned to the right
device on the I2C bus.

Signed-off-by: Johannes Hahn <johannes-hahn@siemens.com>
Co-developed-by: Claudius Heine <ch@denx.de>
Signed-off-by: Claudius Heine <ch@denx.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210317075228.683184-1-ch@denx.de