mach-imx: bootaux: print stack pointer and reset vector

1. Change information printed about loaded M4 binary, print the stack
pointer and reset vector addressed.
2. Add sanity check for the address provided as param.
Signed-off-by: NIgor Opaniuk <igor.opaniuk@toradex.com>
Reviewed-by: NOleksandr Suvorov <oleksandr.suvorov@toradex.com>

arch/arm/mach-imx/imx_bootaux.c

@@ -20,6 +20,9 @@ int arch_auxiliary_core_up(u32 core_id, ulong boot_private_data)
 	stack = *(u32 *)boot_private_data;
 	pc = *(u32 *)(boot_private_data + 4);
 
+	printf("## Starting auxiliary core stack = 0x%08lX, pc = 0x%08lX...\n",
+	       stack, pc);
+
 	/* Set the stack and pc to M4 bootROM */
 	writel(stack, M4_BOOTROM_BASE_ADDR);
 	writel(pc, M4_BOOTROM_BASE_ADDR + 4);
@@ -80,7 +83,8 @@ static int do_bootaux(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 
 	addr = simple_strtoul(argv[1], NULL, 16);
 
-	printf("## Starting auxiliary core at 0x%08lX ...\n", addr);
+	if (!addr)
+		return CMD_RET_FAILURE;
 
 	ret = arch_auxiliary_core_up(0, addr);
 	if (ret)