ARM: dts: AM4372: Add the am4372-rtc compatible string

am4372-rtc string was already part of dts, introduced to identify
the rtc specific to am4372 family of SoCs. It was removed in one of the
previous patches. Adding back the same with appropriate documentation.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
diff --git a/Documentation/devicetree/bindings/rtc/rtc-omap.txt b/Documentation/devicetree/bindings/rtc/rtc-omap.txt
index 4ba4dbd..43a8366 100644
--- a/Documentation/devicetree/bindings/rtc/rtc-omap.txt
+++ b/Documentation/devicetree/bindings/rtc/rtc-omap.txt
@@ -8,6 +8,7 @@
 			    Wakeup generation for event Alarm. It can also be
 			    used to control an external PMIC via the
 			    pmic_power_en pin.
+	- "ti,am4372-rtc" - for RTC IP used similar to that on AM437X SoC family.
 - reg: Address range of rtc register set
 - interrupts: rtc timer, alarm interrupts in order
 - interrupt-parent: phandle for the interrupt controller