powerpc/fsl: Update fman dt binding with pcs-phy and tbi-phy

The FMan contains internal PHY devices used for SGMII connections
to external PHYs. When these PHYs are in use a reference is needed
for both the external PHY and the internal one. For the external
PHY phy-handle provides the reference. For the internal PHY a new
handle is required.
In dTSEC, the internal PHY is a TBI (Ten Bit Interface) PHY,
the handle used will be tbi-handle.
In mEMAC, the internal PHY is a PCS (Physical Coding Sublayer) PHY,
the handle used will be pcsphy-handle.

Signed-off-by: Igal Liberman <igal.liberman@freescale.com>
Signed-off-by: Scott Wood <oss@buserror.net>