ARM: dts: omap3-gta04: tvout: enable as display1 alias

The omap dss susbystem takes the display aliases to find
out which displays exist. To enable tv-out we must define
an alias.

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>