feat(imx8mn): optionally take params from BL2

Optionally take params from BL2 to offer more flexibility to BL2 on
where and if a BL32 image is expected. This uses imx_bl31_params_parse()
to check if arg0 can safely be accessed as a pointer and actually
contains a bl_params_t structure. If not, the hardcoded parameter
values are used as before.

Change-Id: Ia12d35778f4d550860e517f2a1f5c5d062f3283a
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/plat/imx/imx8m/imx8mn/platform.mk b/plat/imx/imx8m/imx8mn/platform.mk
index a571e28..87b3a6f 100644
--- a/plat/imx/imx8m/imx8mn/platform.mk
+++ b/plat/imx/imx8m/imx8mn/platform.mk
@@ -25,7 +25,8 @@
 				plat/common/plat_psci_common.c		\
 				plat/imx/common/plat_imx8_gic.c
 
-BL31_SOURCES		+=	plat/imx/common/imx8_helpers.S			\
+BL31_SOURCES		+=	common/desc_image_load.c			\
+				plat/imx/common/imx8_helpers.S			\
 				plat/imx/imx8m/gpc_common.c			\
 				plat/imx/imx8m/imx_hab.c			\
 				plat/imx/imx8m/imx_aipstz.c			\