omapfb: lcd_ams_delta: drive control lines over GPIO

Don't use Amstrad Delta custom I/O functions any longer, use GPIO API
instead.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Acked-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>