mtd: nand: pxa3xx: Remove unneeded ifdef CONFIG_OF

There's no need to enclose this code within idef CONFIG_OF,
because the OF framework provides no-op stubs if CONFIG_OF=n.

Cc: devicetree@vger.kernel.org
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Olof Johansson <olof@lixom.net>