ARM: shmobile: remove paragraph on DT reference platforms

They have all been eliminated now.
Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

Documentation/devicetree/bindings/arm/shmobile.txt

@@ -55,7 +55,3 @@ Boards:
     compatible = "renesas,lager", "renesas,r8a7790"
   - Marzen
     compatible = "renesas,marzen", "renesas,r8a7779"
-
-Note: Reference Device Tree Implementations are temporary implementations
-      to ease the migration from platform devices to Device Tree, and are
-      intended to be removed in the future.