dt-bindings: reset: rcar-rst: Document r8a774b1 reset module

Document bindings for the RZ/G2N (R8A774B1) reset module.
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Link: https://lore.kernel.org/r/1568881036-4404-4-git-send-email-biju.das@bp.renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Documentation/devicetree/bindings/reset/renesas,rst.txt

@@ -20,6 +20,7 @@ Required properties:
 		  - "renesas,r8a7745-rst" (RZ/G1E)
 		  - "renesas,r8a77470-rst" (RZ/G1C)
 		  - "renesas,r8a774a1-rst" (RZ/G2M)
+		  - "renesas,r8a774b1-rst" (RZ/G2N)
 		  - "renesas,r8a774c0-rst" (RZ/G2E)
 		  - "renesas,r8a7778-reset-wdt" (R-Car M1A)
 		  - "renesas,r8a7779-reset-wdt" (R-Car H1)