imx: ventana: correct splashimage load address

imx: ventana: correct splashimage load address

Commit 72d81360aabd ("global: Convert CONFIG_LOADADDR to
CONFIG_SYS_LOADADDR") dropped the usage of LOADADDR and replaced it with
SYS_LOADADDR.

Use the correct macro in environment by replacing CONFIG_LOADADDR with
CONFIG_SYS_LOADADDR.

Fixes: d75ebf3482c3 ("imx: ventana: fix splash logo drawing")
Signed-off-by: Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>
Cc: Tim Harvey <tharvey@gateworks.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Acked-By: Tim Harvey <tharvey@gateworks.com>