arm: bcm235xx: implement the boot0 hook code

Choose the Kconfig boot0 hook option and implement the required code.

Signed-off-by: Steve Rae <srae@broadcom.com>

arch/arm/include/asm/arch-bcm235xx/boot0.h

+/*
+ * Copyright 2016 Broadcom Corporation.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __BOOT0_H
+#define __BOOT0_H
+
+/* BOOT0 header information */
+#define ARM_SOC_BOOT0_HOOK	\
+	.word	0xbabeface;	\
+	.word	_end - _start
+
+#endif /* __BOOT0_H */

configs/bcm23550_w1d_defconfig

 CONFIG_ARM=y
+CONFIG_ENABLE_ARM_SOC_BOOT0_HOOK=y
 CONFIG_TARGET_BCM23550_W1D=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y