configs: verdin-imx8m[mp]: set CONFIG_SPL_LOAD_FIT_ADDRESS

Set the CONFIG_SPL_LOAD_FIT_ADDRESS for both verdin-imx8mm and
verdin-imx8mp configurations to specify the load address for FIT images
loaded by the SPL.

As per lastest instructions from NXP, the generation of a HABv4 CSF
(Command Sequence File) requires the U-Boot FIT image (u-boot.itb) load
address to be set to a fixed value when binman is used. The address is
defined by CONFIG_SPL_LOAD_FIT_ADDRESS.

Here we set CONFIG_SPL_LOAD_FIT_ADDRESS to an address 64MB past the
start of the DDR memory leaving plenty of room for the various DDR-
residing artifacts to be moved to their usual load addresses which are
close to the start of the DDR.

Signed-off-by: Rogerio Guerra Borin <rogerio.borin@toradex.com>
Signed-off-by: Hiago De Franco <hiago.franco@toradex.com>
Acked-by: Francesco Dolcini <francesco.dolcini@toradex.com>