rtc: pcf2123: add proper compatible string

nxp,rtc-pcf2123 is not a proper compatible strong for this RTC. The part
name is only pcf2123 and is less confusing.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20190819182656.29744-9-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

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

 NXP PCF2123 SPI Real Time Clock
 
 Required properties:
-- compatible: should be: "nxp,rtc-pcf2123"
+- compatible: should be: "nxp,pcf2123"
                       or "microcrystal,rv2123"
 - reg: should be the SPI slave chipselect address
 
@@ -11,7 +11,7 @@ Optional properties:
 Example:
 
 pcf2123: rtc@3 {
-	compatible = "nxp,rtc-pcf2123"
+	compatible = "nxp,pcf2123"
 	reg = <3>
 	spi-cs-high;
 };

drivers/rtc/rtc-pcf2123.c

@@ -443,8 +443,10 @@ static int pcf2123_probe(struct spi_device *spi)
 
 #ifdef CONFIG_OF
 static const struct of_device_id pcf2123_dt_ids[] = {
-	{ .compatible = "nxp,rtc-pcf2123", },
+	{ .compatible = "nxp,pcf2123", },
 	{ .compatible = "microcrystal,rv2123", },
+	/* Deprecated, do not use */
+	{ .compatible = "nxp,rtc-pcf2123", },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, pcf2123_dt_ids);