hisilicon: hi6220: Add a hi6220 pinmux driver.

This patch adds basic pinmux support for the hi6220 SoC,
which is found on the hikey board.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
diff --git a/arch/arm/cpu/armv8/Makefile b/arch/arm/cpu/armv8/Makefile
index 6466ebb..adb11b3 100644
--- a/arch/arm/cpu/armv8/Makefile
+++ b/arch/arm/cpu/armv8/Makefile
@@ -17,3 +17,4 @@
 
 obj-$(CONFIG_FSL_LSCH3) += fsl-lsch3/
 obj-$(CONFIG_ARCH_ZYNQMP) += zynqmp/
+obj-$(CONFIG_TARGET_HIKEY) += hisilicon/