ARM: omap/fb: move omap_init_fb to .init.text

omap_init_fb() is only called as arch_initcall and so can live in
.init.text.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>