mtd: nand: sh_flctl: Remove unneeded CONFIG_OF

Since the of_mtd header provides dummy stubs for !CONFIG_OF, it's safe
to remove the #ifdef CONFIG_OF. Build tested only.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>