compat: rename MDIO exported symbols

compat: rename MDIO exported symbols

compat-drivers now has support for carrying over the
MDIO module. To help it avoid clashes with already in
place drivers that rely on the older MDIO module we
rename the exported symbols of the shinier module with
a compat_ prefix.

An alternative to this strategy is to have compat-drivers
work under a separate namespace but we have yet to receive
patches for that, although we hear someone did it.

Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>