net: add hifemac Ethernet driver for HiSilicon platform

It adds the driver for HIFEMAC Ethernet controller found on HiSilicon
SoCs like Hi3798MV200.  It's based on the mainstream linux driver, but
quite a lot of code gets rewritten and cleaned up to adopt u-boot driver
model.

Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
diff --git a/drivers/net/Makefile b/drivers/net/Makefile
index 1d444f5..65603b0 100644
--- a/drivers/net/Makefile
+++ b/drivers/net/Makefile
@@ -47,6 +47,7 @@
 obj-$(CONFIG_FTGMAC100) += ftgmac100.o
 obj-$(CONFIG_FTMAC100) += ftmac100.o
 obj-$(CONFIG_GMAC_ROCKCHIP) += gmac_rockchip.o
+obj-$(CONFIG_HIFEMAC_ETH) += hifemac.o
 obj-$(CONFIG_HIGMACV300_ETH) += higmacv300.o
 obj-$(CONFIG_KS8851_MLL) += ks8851_mll.o
 obj-$(CONFIG_KSZ9477) += ksz9477.o