doc: sl-mx8mm: Remove ATF_LOAD_ADDR export

imx8mm-u-boot.dtsi passes the ATF load address via the
'entry' and 'load' properties.

Remove the step that performs the ATF_LOAD_ADDR export, which is
now unneeded.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Patrick Wildt <patrick@blueri.se>
1 file changed