doc: boards: amlogic: update for Odroid HC4

Add documentation bits for the Odroid-HC4.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/doc/board/amlogic/odroid-c4.rst b/doc/board/amlogic/odroid-c4.rst
index 5a5a868..f66d60a 100644
--- a/doc/board/amlogic/odroid-c4.rst
+++ b/doc/board/amlogic/odroid-c4.rst
@@ -17,6 +17,9 @@
  - UART serial
  - Infrared receiver
 
+The ODROID-HC4 is a variant with a PCIe-SATA controller, the same commands
+applies for HC4.
+
 Schematics are available on the manufacturer website.
 
 U-Boot compilation