Documentation: fsl-mc: binding updates for MSIs, ranges, PHYs

-The Freescale Management Complex and all associated objects
 use message interrupts, and thus an msi-parent is required.

-Define a ranges property to specify the mapping between
 the MC address space and the system address space.

-The fsl-mc node may optionally have dpmac sub-nodes that describe
 the relationship between the Ethernet MACs which belong to the MC
 and the Ethernet PHYs on the system board.

Signed-off-by: Stuart Yoder <stuart.yoder@nxp.com>
Acked-by: J. German Rivera <German.Rivera@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>