rtc: pcf2123: Add Microcrystal rv2123

Add a compatible string for Microcrystal rv2123 as the reset procedure seem
to be differing. However, the current driver works just fine.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/nxp,rtc-2123.txt

@@ -2,6 +2,7 @@ NXP PCF2123 SPI Real Time Clock
 
 Required properties:
 - compatible: should be: "nxp,rtc-pcf2123"
+                      or "microcrystal,rv2123"
 - reg: should be the SPI slave chipselect address
 
 Optional properties:

drivers/rtc/rtc-pcf2123.c

@@ -453,6 +453,7 @@ static int pcf2123_remove(struct spi_device *spi)
 #ifdef CONFIG_OF
 static const struct of_device_id pcf2123_dt_ids[] = {
 	{ .compatible = "nxp,rtc-pcf2123", },
+	{ .compatible = "microcrystal,rv2123", },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, pcf2123_dt_ids);