Documentation: devicetree: amlogic: Document P20x and ODROID-C2 boards

Add compatible strings for Amlogic S905/GXBB based boards: Hardkernel
ODROID-C2, Amlogic P200 and Amlogic P201.

Cc: devicetree@vger.kernel.org
Reviewed-by: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NKevin Hilman <khilman@baylibre.com>
Acked-by: NRob Herring <robh@kernel.org>
Acked-by: NArnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/arm/amlogic.txt

@@ -25,3 +25,6 @@ Board compatible values:
   - "tronsmart,vega-s95-pro", "tronsmart,vega-s95" (Meson gxbb)
   - "tronsmart,vega-s95-meta", "tronsmart,vega-s95" (Meson gxbb)
   - "tronsmart,vega-s95-telos", "tronsmart,vega-s95" (Meson gxbb)
+  - "hardkernel,odroid-c2" (Meson gxbb)
+  - "amlogic,p200" (Meson gxbb)
+  - "amlogic,p201" (Meson gxbb)