video: omapfb: fix missing #includes

The omapfb driver fails to build after commit 23c35f48
("pinctrl: remove include file from <linux/device.h>") because it
relies on the <linux/pinctrl/consumer.h> and <linux/seq_file.h>
being pulled in by the <linux/device.h> header implicitly.

Include these headers explicitly to avoid the build failures.

Fixes: 23c35f48

 ("pinctrl: remove include file from <linux/device.h>")
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Tested-by: Tony Lindgren <tony@atomide.com>
[b.zolnierkie: fix include order and patch description]
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>