board: odroid-n2: Update docs for signing

The previous instructions resulted in a bootloader that wouldn't fit in
an MBR gap. I have updated the docs based on upstream's build process.

Signed-off-by: Baltazár Radics <baltazar.radics@gmail.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20250110111335.9221-1-baltazar.radics@gmail.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
1 file changed