ARM: dts: mapphone: separate out xt894 specific things

Remove xt894 specific things from motorola-mapphone-common.dtsi and add
them to omap4-droid4-xt894.dts and omap4-droid-bionic-xt875.dts as
applicable.

Signed-off-by: Carl Philipp Klemm <philipp@uvos.xyz>
[tony@atomide.com: shortened subject, wrapped description]
Signed-off-by: Tony Lindgren <tony@atomide.com>