ARM: dts: gta04: Move model property out of pinctrl node

The model property should be at the top level, let's move it out
of the pinctrl node.

Fixes: d2eaf949 ("ARM: dts: omap3-gta04a5one: define GTA04A5 variant with OneNAND")
Cc: Andreas Kemnade <andreas@kemnade.info>
Cc: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>