ARM: OMAP2+: Remove gpmc-onenand

As OneNAND driver is now using devicetree gpmc-onenand and its
platform data is unused and can be removed.

Signed-off-by: Ladislav Michl <ladis@linux-mips.org>
Reviewed-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>