doc: boards: amlogic: add documentation for ODROID-HC4

Add separate documentation for the ODROID-HC4 board to ensure
users build U-Boot using the HC4 defconfig that enables PCIe
SATA boot. This avoids user frustration trying to boot after
using the C4 recipe which only works from SD card.

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Link: https://lore.kernel.org/r/20230320114609.930145-34-christianshewitt@gmail.com
[narmstrong: fixed doc build]
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
2 files changed