serial: sh-sci: Add device tree support for r8a7794

Simply document the new compat string.
There appears to be no need for a driver update.

Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
[geert: Reworded to match previous commits]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/renesas,sci-serial.txt

@@ -20,6 +20,10 @@ Required properties:
     - "renesas,scifa-r8a7791" for R8A7791 (R-Car M2) SCIFA compatible UART.
     - "renesas,scifb-r8a7791" for R8A7791 (R-Car M2) SCIFB compatible UART.
     - "renesas,hscif-r8a7791" for R8A7791 (R-Car M2) HSCIF compatible UART.
+    - "renesas,scif-r8a7794" for R8A7794 (R-Car E2) SCIF compatible UART.
+    - "renesas,scifa-r8a7794" for R8A7794 (R-Car E2) SCIFA compatible UART.
+    - "renesas,scifb-r8a7794" for R8A7794 (R-Car E2) SCIFB compatible UART.
+    - "renesas,hscif-r8a7794" for R8A7794 (R-Car E2) HSCIF compatible UART.
     - "renesas,scif" for generic SCIF compatible UART.
     - "renesas,scifa" for generic SCIFA compatible UART.
     - "renesas,scifb" for generic SCIFB compatible UART.