video: imxfb: Remove dead declaration of set_imx_fb_info()

Function set_imx_fb_info() is missing in the kernel code,
so remove the dead declaration.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>