imx8mm_evk: adjust dram size in case bl32 is used

Adjust DRAM size in case BL32 secure payload is loaded (OP-TEE/Trusty),
so during MMU initialization U-Boot won't touch this mem area.

BL32 is loaded to the end of DRAM, bl32 payload size is read from
rom_pointer[1]. This relates to the issue described in
59efa6b52b("imx8m: Fix MMU table issue for OPTEE memory").

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
diff --git a/board/freescale/imx8mm_evk/imx8mm_evk.c b/board/freescale/imx8mm_evk/imx8mm_evk.c
index c5fd940..53ebb94 100644
--- a/board/freescale/imx8mm_evk/imx8mm_evk.c
+++ b/board/freescale/imx8mm_evk/imx8mm_evk.c
@@ -15,7 +15,11 @@
 
 int dram_init(void)
 {
-	gd->ram_size = PHYS_SDRAM_SIZE;
+	/* rom_pointer[1] contains the size of TEE occupies */
+	if (rom_pointer[1])
+		gd->ram_size = PHYS_SDRAM_SIZE - rom_pointer[1];
+	else
+		gd->ram_size = PHYS_SDRAM_SIZE;
 
 	return 0;
 }