The LCD regulator and backlight are specific only to droid bionic xt875
and droid4 xt894. On droid razr xt910 and xt912, the LCD regulator and
backlight are different. The LCD and backlight are also different on the
the mz609 tablets.

Let's add a common motorola-mapphone-xt8xx.dtsi to make it easy to add
support for xt910 and xt912 and the mz609 to mz617 tablets.

While at it, let's also move aliases to the board specific dts files where
they belong. And let's move the omap4-droid4-xt894.dts compatible to the
top.
Signed-off-by: Tony Lindgren <tony@atomide.com>