drm/omapdrm: Fix trivial spelling

Fix trivial spelling identified while examining the code.

	s/supprted./supported./

Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191209123320.10186-1-kieran.bingham+renesas@ideasonboard.com