thermal: rcar: Add binding docs for new R-Car Gen2 SoCs

  - r8a7792 (R-Car V2H)
  - r8a7793 (R-Car M2-N)
  - r8a7794 (R-Car E2)

r8a7791 is now called "R-Car M2-W".

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Documentation/devicetree/bindings/thermal/rcar-thermal.txt

@@ -7,7 +7,10 @@ Required properties:
 			    - "renesas,thermal-r8a73a4" (R-Mobile AP6)
 			    - "renesas,thermal-r8a7779" (R-Car H1)
 			    - "renesas,thermal-r8a7790" (R-Car H2)
-			    - "renesas,thermal-r8a7791" (R-Car M2)
+			    - "renesas,thermal-r8a7791" (R-Car M2-W)
+			    - "renesas,thermal-r8a7792" (R-Car V2H)
+			    - "renesas,thermal-r8a7793" (R-Car M2-N)
+			    - "renesas,thermal-r8a7794" (R-Car E2)
 - reg			: Address range of the thermal registers.
 			  The 1st reg will be recognized as common register
 			  if it has "interrupts".