km/ls102xa: use unused scratchrw4 address for post word

km/ls102xa: use unused scratchrw4 address for post word

The SCRATCHRW4 is only used in secure boot scenario that is unsupported by
our design, so this address can be stolen for storing POST status.
The SCRATCHRW4 is initialized to zero at core rest.

Using a DDR address was unfortunate choice, the DDR at boot time has a
random contend and it happens that sometimes is matching POST magic number.
This behavior can lead to undefined POST behavior and u-boot ending in
failbootcmd command.

Signed-off-by: Aleksandar Gerasimovski <aleksandar.gerasimovski@hitachienergy.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>