board: arbel: Limit the dram effective size to bank0 maximal size

For 4GB dram size, the dram is divided into 2 banks and
the address space of these 2 banks are not concatenated.
Limit the gd->ram_top to not exceed bank0 top to prevent
accessing invalid memory region.

Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>
diff --git a/board/nuvoton/arbel_evb/arbel_evb.c b/board/nuvoton/arbel_evb/arbel_evb.c
index 8fc56c1..53c931c 100644
--- a/board/nuvoton/arbel_evb/arbel_evb.c
+++ b/board/nuvoton/arbel_evb/arbel_evb.c
@@ -27,6 +27,15 @@
 	return 0;
 }
 
+phys_size_t get_effective_memsize(void)
+{
+	/* Use bank0 only */
+	if (gd->ram_size > DRAM_2GB_SIZE)
+		return DRAM_2GB_SIZE;
+
+	return gd->ram_size;
+}
+
 int dram_init(void)
 {
 	struct npcm_gcr *gcr = (struct npcm_gcr *)NPCM_GCR_BA;
@@ -70,21 +79,16 @@
 		gd->bd->bi_dram[1].start = DRAM_4GB_SIZE;
 		gd->bd->bi_dram[1].size = DRAM_2GB_SIZE -
 			(DRAM_4GB_SIZE - DRAM_4GB_ECC_SIZE);
-		/* use bank0 only */
-		gd->ram_size = DRAM_2GB_SIZE;
 		break;
 	case DRAM_4GB_SIZE:
 		gd->bd->bi_dram[0].size = DRAM_2GB_SIZE;
 		gd->bd->bi_dram[1].start = DRAM_4GB_SIZE;
 		gd->bd->bi_dram[1].size = DRAM_2GB_SIZE;
-		/* use bank0 only */
-		gd->ram_size = DRAM_2GB_SIZE;
 		break;
 	default:
 		gd->bd->bi_dram[0].size = DRAM_1GB_SIZE;
 		gd->bd->bi_dram[1].start = 0;
 		gd->bd->bi_dram[1].size = 0;
-		gd->ram_size = DRAM_1GB_SIZE;
 		break;
 	}