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>
diff --git a/configs/bcm23550_w1d_defconfig b/configs/bcm23550_w1d_defconfig
index cd47cd0..0ef4a37 100644
--- a/configs/bcm23550_w1d_defconfig
+++ b/configs/bcm23550_w1d_defconfig
@@ -1,4 +1,5 @@
 CONFIG_ARM=y
+CONFIG_ENABLE_ARM_SOC_BOOT0_HOOK=y
 CONFIG_TARGET_BCM23550_W1D=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y