[POWERPC] 85xx: MPC85xx MDS - Unconditionally select PHYLIB for board fixups

The MPC85xx MDS board requires some board level tweaks of the PHYs that
either the eTSEC (gianfar) or UCC ethernet controllers are connected to.

Its possible to build the phylib as a module, however this breaks the
board level fix ups because phy_read and phy_write are not available
if we build as a module.

So we unconditionally select PHYLIB to ensure its built into the kernel
if we are building in MPC85xx MDS support.  This was determined to be
the easiest soultion even though it prevents the user from removing
PHYLIB support if they decide they don't want it.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>