ARM: dts: gta04: add ldo 3v3 regulator

Required for completeness sake to be able to specify
a regulator for devices having a non-optional regulator
property. It corresponds to the "3V3" net in the
schematics.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>