ARM: dts: motorola-mapphone: Add basic support for mz609 and mz617

ARM: dts: motorola-mapphone: Add basic support for mz609 and mz617

The Motorola mapphone tablets are similar to the mapphone phones, but with
different display and without some phone related peripherals.

Let's add a new motorola-mapphone-mz607-mz617.dtsi and basic files for
xyboard mz609 and mz617. All the tablets from mz607 to mz617 are quite
similar so let's use motorola-mapphone-mz607-mz617.dtsi naming for the
common file.

Note that the tc358765 lcd bridge needs driver changes before it can be
added.

Signed-off-by: Tony Lindgren <tony@atomide.com>