arm: add support for Hisilicon HiSTB family SoCs

First supported chip is hi3798mv200 (which is similar to Hi3798cv200
used by poplar).

Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index ac602ae..5ebe061 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -61,6 +61,7 @@
 machine-$(CONFIG_ARCH_EXYNOS)		+= exynos
 machine-$(CONFIG_ARCH_GXP)		+= hpe
 machine-$(CONFIG_ARCH_HIGHBANK)		+= highbank
+machine-$(CONFIG_ARCH_HISTB)		+= histb
 machine-$(CONFIG_ARCH_IPQ40XX)		+= ipq40xx
 machine-$(CONFIG_ARCH_K3)		+= k3
 machine-$(CONFIG_ARCH_KEYSTONE)		+= keystone