dt-bindings: rtc: sun6i-rtc: Export internal RC oscillator

Experiments showed that on at least the H3/H5/A64 the RTC's internal
oscillator also feeds the CPUS mux in the PRCM.

Export this clock through the device tree, instead of having to use
a dummy fixed-clock device node, for the PRCM to consume. This will
properly describe the relationship between the clocks.
Tested-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/sun6i-rtc.txt

@@ -24,7 +24,7 @@ Required properties:
 
 Required properties for new device trees
 - clocks	: phandle to the 32kHz external oscillator
-- clock-output-names : names of up to two clock outputs. See below.
+- clock-output-names : names of up to three clock outputs. See below.
 - #clock-cells  : must be equal to 1.
 
 The RTC provides the following clocks at the given indices:
@@ -32,6 +32,7 @@ The RTC provides the following clocks at the given indices:
 - 1: LOSC external output, known as X32KFOUT in the datasheet.
      This clock is not available on the A31 and is deprecated for old
      device trees still using the "allwinner,sun6i-a31-rtc" compatible.
+- 2: InternalOSC, or internal RC oscillator (A64/H3/H5 only)
 
 Example: