thermal: rcar: Remove binding docs for r8a7794

The latest information that I have is that there is no thermal IP
block present on the r8a7794 SoC so remove the corresponding binding.

Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

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

@@ -11,7 +11,6 @@ Required properties:
 			    - "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".