ARM: dts: Add minimal support for Droid Bionic xt875

We already have folks booting Droid Bionic with Droid 4 dts, but it is
a different hardware with no keyboard.

Let's start adding device specific support for Droid bionic by making
current omap4-droid4-xt894 a common file and including it.

Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Sebastian Reichel <sre@kernel.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Tony Lindgren <tony@atomide.com>