Currently, all MTD drivers/sublayers exposing an OOB area are
doing the same kind of test to extract the available OOB size
based on the mtd_info and mtd_oob_ops structures.
Move this common logic into an inline function and make use of it.
Signed-off-by: NBoris Brezillon <boris.brezillon@free-electrons.com>
Suggested-by: NPriit Laes <plaes@plaes.org>
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>