mdio: Export mdio.h to userland

The ID packing definitions are needed by userland and the register
definitions may also be useful there.

Do not export mdio_phy_id_{is_c45,prtad,devad}() as the use of bool is
problematic and it's not that useful to export only a subset of these.

Do not export MDIO_SUPPORTS_{C22,C45} directly; these flags are only
exposed to userland through struct ethtool_cmd so they should be
defined alongside that with appropriate names.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index c94e717..4b0b7ed 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -238,6 +238,7 @@
 header-y += major.h
 header-y += map_to_7segment.h
 header-y += matroxfb.h
+header-y += mdio.h
 header-y += media.h
 header-y += mempolicy.h
 header-y += meye.h