Add mdio command for new PHY infrastructure

The new mdio command doesn't have all of the features of the mii
command, but it provides the necessary read/write primitives, and allows
users to interact with 10G PHYs, and other PHYs which use Clause 45 of
802.3.  This means that the mdio command requires a "Device Address"
argument, though for clause 22 PHYs, the argument can be "-".

Signed-off-by: Andy Fleming <afleming@freescale.com>
Acked-by: Detlev Zundel <dzu@denx.de>
diff --git a/common/Makefile b/common/Makefile
index 02dbeed..5f0c534 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -117,6 +117,9 @@
 COBJS-$(CONFIG_CMD_MII) += miiphyutil.o
 COBJS-$(CONFIG_PHYLIB) += miiphyutil.o
 COBJS-$(CONFIG_CMD_MII) += cmd_mii.o
+ifdef CONFIG_PHYLIB
+COBJS-$(CONFIG_CMD_MII) += cmd_mdio.o
+endif
 COBJS-$(CONFIG_CMD_MISC) += cmd_misc.o
 COBJS-$(CONFIG_CMD_MMC) += cmd_mmc.o
 COBJS-$(CONFIG_MP) += cmd_mp.o