imx: imx8mm: kontron: Use maximum DDR size of 3G + 5G = 8G

If less than 8G is available on the board, we detect it at
runtime.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>

include/configs/kontron_common.h

@@ -37,7 +37,9 @@
  */
 #ifdef CONFIG_IMX8M
 #define PHYS_SDRAM			DDR_CSD1_BASE_ADDR
-#define PHYS_SDRAM_SIZE			SZ_2G
+#define PHYS_SDRAM_SIZE			(SZ_2G + SZ_1G)
+#define PHYS_SDRAM_2			0x100000000
+#define PHYS_SDRAM_2_SIZE		(SZ_4G + SZ_1G)
 #define CONFIG_SYS_SDRAM_BASE		PHYS_SDRAM
 #else
 #define PHYS_SDRAM			MMDC0_ARB_BASE_ADDR