ARM: dts: Disable MDMA1 node for arndale-octa board

MDMA1 can support both secure and non-secure AXI transactions. When this
is enabled in the kernel for boards that run in secure mode, we get
imprecise external aborts causing the kernel to oops.

Unhandled fault: imprecise external abort (0x1406) at 0x00000000
Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000007
Suggested-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Tested-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/boot/dts/exynos5420-arndale-octa.dts

@@ -361,4 +361,16 @@ wakeup {
 			gpio-key,wakeup;
 		};
 	};
+
+	amba {
+		mdma1: mdma@11C10000 {
+			/*
+			 * MDMA1 can support both secure and non-secure
+			 * AXI transactions. When this is enabled in the kernel
+			 * for boards that run in secure mode, we are getting
+			 * imprecise external aborts causing the kernel to oops.
+			 */
+			status = "disabled";
+		};
+	};
 };