vexpress64: use 2nd DRAM bank only on juno

This patch makes the 2nd DRAM bank available on Juno only and not on
other vexpress64 targets, eg. the FVP models.

The commit below added a 2nd bank of NOR flash for Juno, but also for
all vexpress64 targets:

    commit 2d0cee1ca2
    Author: Liviu Dudau <Liviu.Dudau@foss.arm.com>
    Date:   Mon Oct 19 11:08:31 2015 +0100

    vexpress64: Juno: Declare all 8GB of RAM and make them visible to the kernel.

    Juno comes with 8GB RAM, but U-Boot only passes 2GB to the kernel.
    Declare a secondary memory bank and set the sizes correctly.

    Signed-off-by: Liviu Dudau <Liviu.Dudau@foss.arm.com>
    Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
    Reviewed-by: Ryan Harkin <ryan.harkin@linaro.org>
    Tested-by: Ryan Harkin <ryan.harkin@linaro.org>

Unfortunately, I only fully tested on Juno R0, R1 and the FVP Foundation
model.  Whilst FVP Base AEMV8 models run U-Boot OK, they fail to boot
the kernel.

Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>
Acked-by: Liviu Dudau <liviu.dudau@foss.arm.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

board/armltd/vexpress64/vexpress64.c

@@ -51,8 +51,10 @@ void dram_init_banksize(void)
 {
 	gd->bd->bi_dram[0].start = PHYS_SDRAM_1;
 	gd->bd->bi_dram[0].size = PHYS_SDRAM_1_SIZE;
+#ifdef PHYS_SDRAM_2
 	gd->bd->bi_dram[1].start = PHYS_SDRAM_2;
 	gd->bd->bi_dram[1].size = PHYS_SDRAM_2_SIZE;
+#endif
 }
 
 /*

include/configs/vexpress_aemv8a.h

@@ -165,15 +165,20 @@
 #define CONFIG_SYS_LOAD_ADDR		(V2M_BASE + 0x10000000)
 
 /* Physical Memory Map */
-#define CONFIG_NR_DRAM_BANKS		2
 #define PHYS_SDRAM_1			(V2M_BASE)	/* SDRAM Bank #1 */
-#define PHYS_SDRAM_2			(0x880000000)
 /* Top 16MB reserved for secure world use */
 #define DRAM_SEC_SIZE		0x01000000
 #define PHYS_SDRAM_1_SIZE	0x80000000 - DRAM_SEC_SIZE
-#define PHYS_SDRAM_2_SIZE	0x180000000
 #define CONFIG_SYS_SDRAM_BASE	PHYS_SDRAM_1
 
+#ifdef CONFIG_TARGET_VEXPRESS64_JUNO
+#define CONFIG_NR_DRAM_BANKS		2
+#define PHYS_SDRAM_2			(0x880000000)
+#define PHYS_SDRAM_2_SIZE		0x180000000
+#else
+#define CONFIG_NR_DRAM_BANKS		1
+#endif
+
 /* Enable memtest */
 #define CONFIG_CMD_MEMTEST
 #define CONFIG_SYS_MEMTEST_START	PHYS_SDRAM_1