powerpc/fsl: Update fman dt binding with clock name and qbman link

The clock name "fmanclk" was given in the example, but not specified
in the binding itself.  Made clock-names mandatory as otherwise there's
not much point having it.

Added a reference to the fsl,qman and fsl,bman properties proposed
in http://patchwork.ozlabs.org/patch/407034/ and
http://patchwork.ozlabs.org/patch/407035/

Signed-off-by: Scott Wood <scottwood@freescale.com>