mtd: nand: sunxi: fix OOB handling in ->write_xxx() functions

mtd: nand: sunxi: fix OOB handling in ->write_xxx() functions

commit 03a0e8a7c5ea29b5c4e72dfd64900b47a8fb6f2d upstream.

The USER_DATA register cannot be accessed using byte accessors on A13
SoCs, thus triggering a bug when using memcpy_toio on this register.
Declare an helper macros to convert an OOB buffer into a suitable
USER_DATA value and vice-versa.

This patch also fixes an error in the oob_required logic (some OOB data
are not written even if the user required it) by removing the
oob_required condition, which is perfectly valid since the core already
fill ->oob_poi with FFs when oob_required is false.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Fixes: 1fef62c1423b ("mtd: nand: add sunxi NAND flash controller support")
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>