Introduce support for U-Boot for Airoha EN7581/AN7583. For EN7581
initial patch are already in U-Boot mainline and doesn't require
backport, for AN7583 some patch are still pending but already posted
upstream.
Also add for now, precompiled binary for ATF BL2 and BL31. Support for
ATF is planned and will come later.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
04f6769a4a