configs: meson: change default load addresses

The original chosen addresses conflict with the BL2 initialisation.
So far there was no issue with them but if we preload binaries in
RAM (ROMUSB boot) before running the BL2 they get corrupted by the
execution of BL2 init.

If we load them around 0x08000000, there is no such issue.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>