Documentation: dt: OMAP: Update Overo/Tobi

Update the compatible string for Overo/Tobi to reflect the latest
changes.

Signed-off-by: Florian Vaussard <florian.vaussard@epfl.ch>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Documentation/devicetree/bindings/arm/omap/omap.txt

@@ -91,7 +91,7 @@ Boards:
   compatible = "ti,omap3-beagle", "ti,omap3"
 
 - OMAP3 Tobi with Overo : Commercial expansion board with daughter board
-  compatible = "ti,omap3-tobi", "ti,omap3-overo", "ti,omap3"
+  compatible = "gumstix,omap3-overo-tobi", "gumstix,omap3-overo", "ti,omap3"
 
 - OMAP4 SDP : Software Development Board
   compatible = "ti,omap4-sdp", "ti,omap4430"