PM / Domains: R-Mobile SYSC: Document R-Mobile APE6 (r8a73a4) binding

R-Mobile APE6 (r8a73a4) is handled fine by the same driver and bindings.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

Documentation/devicetree/bindings/power/renesas,sysc-rmobile.txt

@@ -11,6 +11,7 @@ Required properties:
 - compatible: Should be "renesas,sysc-<soctype>", "renesas,sysc-rmobile" as
 	      fallback.
 	      Examples with soctypes are:
+		- "renesas,sysc-r8a73a4" (R-Mobile APE6)
 		- "renesas,sysc-r8a7740" (R-Mobile A1)
 		- "renesas,sysc-sh73a0" (SH-Mobile AG5)
 - reg: Two address start and address range blocks for the device: